Driving Frustum Desk from code

Everything the web app does is available over HTTP. The base URL is https://api.skillsafe.ai/v1/app-api, every request carries Authorization: Bearer <token>, and every response is the same envelope.

The `task` field comes first

This app has five lanes behind one endpoint. Every run body must carry a task field naming the lane - it is what the system prompt routes on. Send the wrong one and you get a valid package of the wrong kind; omit it and the model picks the closest lane and tells you which it chose.

One more shape trap: the run body is the input object. Do not wrap it in an {"input": ...} envelope - that returns 200 while hiding task from the model, which is the most confusing way this API can fail.

task Lane Fields Sections returned

plan Turn a shot description into a camera brief, known Summary, The Sheet, The Numbers, Reasoning, Next Step

audit What this camera can see, resolve, and is drawing for nothing sheet, worry Summary, Verdict, Findings, Corrected Sheet, Next Step

frame One vertical angle, many horizontals sheet Summary, Every Canvas, What Fits Where, The Camera Distance, Next Step

depth near, far, and what cannot be separated sheet Summary, The Depth Ladder, What Cannot Be Separated, The Second Frustum, Next Step

decide Decide what changes: a number, the scene, or the shot sheet, fixed Summary, A Number Fixes, Only A Re-Author Fixes, Nothing Fixes, Next Step

task	Lane	Fields	Sections returned
`plan`	Turn a shot description into a camera	`brief, known`	Summary, The Sheet, The Numbers, Reasoning, Next Step
`audit`	What this camera can see, resolve, and is drawing for nothing	`sheet, worry`	Summary, Verdict, Findings, Corrected Sheet, Next Step
`frame`	One vertical angle, many horizontals	`sheet`	Summary, Every Canvas, What Fits Where, The Camera Distance, Next Step
`depth`	near, far, and what cannot be separated	`sheet`	Summary, The Depth Ladder, What Cannot Be Separated, The Second Frustum, Next Step
`decide`	Decide what changes: a number, the scene, or the shot	`sheet, fixed`	Summary, A Number Fixes, Only A Re-Author Fixes, Nothing Fixes, Next Step

Only task and the lane's own required fields are mandatory: sheet on audit, frame, depth and decide; brief on plan. Every field is a string - there are no number fields on this app. sheet is the scene sheet itself: a header of KEY: value lines, an OBJECTS: block and an optional LIGHTS: block.

fov is the VERTICAL angle - three.js's PerspectiveCamera(fov, aspect, near, far) takes one, and every renderer that resizes to its element recomputes aspect from the canvas on every resize. So there is no horizontal field of view to set; there is only the one the canvas gives you, and it is 2 × atan(tan(fov ÷ 2) × aspect). The vertical framing is identical on every canvas and the horizontal is not, which is why CANVAS takes a comma list.

near is the dial and far very nearly is not. The smallest separation a B-bit fixed-point depth buffer can resolve at view distance z is z² × (1/near − 1/far) ÷ (2^B − 1), and once far is much larger than near the second term is already negligible. Raising near ten-fold buys ten-fold precision at every distance; lowering far ten-fold buys about a hundredth of a percent. State near even when nothing else is known - it is assumed 0.1, and it decides every precision figure in the answer.

DEPTH is one of 16, 24, 32 or log. The first three are fixed-point; log is three.js's logarithmicDepthBuffer, which makes the error linear in distance rather than quadratic - far-field precision improves enormously, near-field precision gets worse, and it costs a per-fragment depth write. It is a trade, not a fix.

An object is <name> <shape> <size> at=x,y,z with shape one of box, plane, sphere or cylinder, sized WxHxD, WxH, R and RxH respectively. feature= names the smallest detail that has to survive; without it the object's own smallest dimension is used. Frustum culling tests the object's circumscribed bounding sphere, not the object, so the answer reports both what is submitted and what is actually visible.

A light with a map= and a span= is a SECOND FRUSTUM. A directional light's shadow camera is orthographic, so its texel density is exactly mapSize ÷ span and is uniform - which means halving the span is worth exactly as much as doubling the map and costs a quarter of the memory. It has its own near and far and obeys the same depth arithmetic, which is what shadow acne actually is.

Anything the reader cannot place is listed as a problem rather than skipped, and so is an object named twice. An object that quietly vanished would be a smaller scene than the one described, and every count and extent in the answer too generous.

An angle is reported in degrees to one place, a distance in world units, a depth step in the smallest readable unit, a ratio as N×, and a pixel count against the DRAWING BUFFER rather than the CSS size. The engine works in angles, distances and bit depths: it has not created a WebGL context, rendered a frame, or measured a GPU.

Add $model to any body to choose the model for that run: gpt-5.6-luna, gpt-5.6-terra (the default) or gpt-5.6-sol. Luna caps output at 4,096 tokens and will fail the audit, frame and depth lanes rather than shorten them - a findings table, a corrected sheet, or a row per object with its depth step and culling verdict, is several thousand characters before the reasoning starts.

The response envelope

Success and failure have the same outer shape, so one check covers both.

{
  "ok": true,
  "data": {
    "...": "the result"
  }
}

{
  "ok": false,
  "error": {
    "code": "VALIDATION_ERROR",
    "message": "seconds should be number, got string",
    "details": {}
  }
}

HTTP error.code What it means

400 VALIDATION_ERROR The body was not a JSON object, or a declared field had the wrong type. A number field sent as a string is the usual cause.

401 UNAUTHORIZED No token, or a token that has expired or been revoked. Mint a new one.

402 INSUFFICIENT_CREDITS The balance is below the run's minimum. Call /estimate first and compare hold_credits against /me.

404 NOT_FOUND Wrong path, or a job id that does not belong to this token.

409 CONFLICT An Idempotency-Key replay whose body differs from the original request.

429 RATE_LIMITED Too many requests. Back off; do not tight-loop.

503 UPSTREAM_UNAVAILABLE The model provider is unavailable. Retry with backoff.

HTTP	error.code	What it means
`400`	`VALIDATION_ERROR`	The body was not a JSON object, or a declared field had the wrong type. A number field sent as a string is the usual cause.
`401`	`UNAUTHORIZED`	No token, or a token that has expired or been revoked. Mint a new one.
`402`	`INSUFFICIENT_CREDITS`	The balance is below the run's minimum. Call /estimate first and compare hold_credits against /me.
`404`	`NOT_FOUND`	Wrong path, or a job id that does not belong to this token.
`409`	`CONFLICT`	An Idempotency-Key replay whose body differs from the original request.
`429`	`RATE_LIMITED`	Too many requests. Back off; do not tight-loop.
`503`	`UPSTREAM_UNAVAILABLE`	The model provider is unavailable. Retry with backoff.

1. Get a token

Open /tokens.html in a browser and copy the token this app already holds - no developer console needed. A guest token is minted automatically and is enough for /me and /estimate; writing a package is metered and needs a personal token, which comes from signing in on that page.

Keep it in an environment variable rather than in source:

export SKILLSAFE_TOKEN="YOUR_TOKEN"

2. Check the session and the balance

GET /me is free. It returns only three fields: subject_type, subject_id and credits. Signed-in means subject_type == "user" - there is no username or email to test.

curl -sS -X GET "https://api.skillsafe.ai/v1/app-api/me" \
  -H "Authorization: Bearer $SKILLSAFE_TOKEN"

import json, urllib.request

TOKEN = "YOUR_TOKEN"   # from /tokens.html
BASE  = "https://api.skillsafe.ai/v1/app-api"

def call(method, path, payload=None, headers=None):
    data = json.dumps(payload).encode() if payload is not None else None
    req = urllib.request.Request(BASE + path, data=data, method=method)
    req.add_header("Authorization", "Bearer " + TOKEN)
    req.add_header("Content-Type", "application/json")
    req.add_header("Accept", "application/json")
    # A plain urllib request with no User-Agent is refused with 403.
    req.add_header("User-Agent", "frustum-desk-client/1.0")
    for k, v in (headers or {}).items():
        req.add_header(k, v)
    with urllib.request.urlopen(req) as r:
        return json.loads(r.read())

out = call("GET", "/me")
print(json.dumps(out["data"], indent=2))

const TOKEN = "YOUR_TOKEN";   // from /tokens.html
const BASE  = "https://api.skillsafe.ai/v1/app-api";

async function call(method, path, payload) {
  const res = await fetch(BASE + path, {
    method,
    headers: {
      "Authorization": `Bearer ${TOKEN}`,
      "Content-Type": "application/json"
    },
    body: payload === undefined ? undefined : JSON.stringify(payload)
  });
  const json = await res.json();
  if (!res.ok || !json.ok) throw new Error(json.error?.message || res.statusText);
  return json.data;
}

const data = await call("GET", "/me");
console.log(data);

package main

import (
	"bytes"
	"fmt"
	"io"
	"net/http"
)

const base = "https://api.skillsafe.ai/v1/app-api"
const token = "YOUR_TOKEN" // from /tokens.html

func main() {
	req, _ := http.NewRequest("GET", base+"/me", nil)
	req.Header.Set("Authorization", "Bearer "+token)
	req.Header.Set("Content-Type", "application/json")
	res, err := http.DefaultClient.Do(req)
	if err != nil {
		panic(err)
	}
	defer res.Body.Close()
	out, _ := io.ReadAll(res.Body)
	fmt.Println(string(out))
}

import java.net.URI;
import java.net.http.*;

public class Main {
    static final String BASE  = "https://api.skillsafe.ai/v1/app-api";
    static final String TOKEN = "YOUR_TOKEN"; // from /tokens.html

    public static void main(String[] args) throws Exception {
        HttpRequest req = HttpRequest.newBuilder()
            .uri(URI.create(BASE + "/me"))
            .header("Authorization", "Bearer " + TOKEN)
            .header("Content-Type", "application/json")
            .method("GET", HttpRequest.BodyPublishers.noBody())
            .build();
        HttpResponse<String> res = HttpClient.newHttpClient()
            .send(req, HttpResponse.BodyHandlers.ofString());
        System.out.println(res.body());
    }
}

require 'net/http'
require 'json'
require 'uri'

BASE  = "https://api.skillsafe.ai/v1/app-api"
TOKEN = "YOUR_TOKEN" # from /tokens.html

uri = URI("#{BASE}/me")
req = Net::HTTP::Get.new(uri)
req["Authorization"] = "Bearer #{TOKEN}"
req["Content-Type"] = "application/json"
res = Net::HTTP.start(uri.hostname, uri.port, use_ssl: true) { |h| h.request(req) }
puts JSON.pretty_generate(JSON.parse(res.body)["data"])

<?php
$base  = "https://api.skillsafe.ai/v1/app-api";
$token = "YOUR_TOKEN"; // from /tokens.html

$opts = ["http" => [
    "method"  => "GET",
    "header"  => "Authorization: Bearer $token\r\nContent-Type: application/json\r\n",
]];
$res  = file_get_contents($base . "/me", false, stream_context_create($opts));
$json = json_decode($res, true);
print_r($json["data"]);

using System.Net.Http;
using System.Text;

const string Base  = "https://api.skillsafe.ai/v1/app-api";
const string Token = "YOUR_TOKEN"; // from /tokens.html

var http = new HttpClient();
http.DefaultRequestHeaders.Add("Authorization", $"Bearer {Token}");

var res = await http.SendAsync(new HttpRequestMessage(new HttpMethod("GET"), Base + "/me")
{
    Content = null
});
Console.WriteLine(await res.Content.ReadAsStringAsync());

3. Price the run before making it

POST /estimate costs nothing, creates no job, and returns the worst-case cost. Compare hold_credits against the balance from step 2 before you submit: a 402 after the fact is avoidable. hold_credits is a reservation priced at the full output cap - the actual charge is usually far lower.

It also echoes model, model_alias and markup_bps, which is the authoritative check that a run is bound to the model you think it is. Estimate each lane separately: their prompts and caps differ, so their holds do.

curl -sS -X POST "https://api.skillsafe.ai/v1/app-api/estimate" \
  -H "Authorization: Bearer $SKILLSAFE_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
  "task": "audit",
  "sheet": "<CANVAS, DPR, CAMERA, DEPTH and OBJECTS/LIGHTS blocks; the grammar is in /llms.txt>",
  "worry": "it graded fine last time and this one will not come clean",
  "rules": "<the working rules for this lane, sent by the app>"
}'

import json, urllib.request

TOKEN = "YOUR_TOKEN"   # from /tokens.html
BASE  = "https://api.skillsafe.ai/v1/app-api"

def call(method, path, payload=None, headers=None):
    data = json.dumps(payload).encode() if payload is not None else None
    req = urllib.request.Request(BASE + path, data=data, method=method)
    req.add_header("Authorization", "Bearer " + TOKEN)
    req.add_header("Content-Type", "application/json")
    req.add_header("Accept", "application/json")
    # A plain urllib request with no User-Agent is refused with 403.
    req.add_header("User-Agent", "frustum-desk-client/1.0")
    for k, v in (headers or {}).items():
        req.add_header(k, v)
    with urllib.request.urlopen(req) as r:
        return json.loads(r.read())

payload = {
  "task": "audit",
  "sheet": "<CANVAS, DPR, CAMERA, DEPTH and OBJECTS/LIGHTS blocks; the grammar is in /llms.txt>",
  "worry": "it graded fine last time and this one will not come clean",
  "rules": "<the working rules for this lane, sent by the app>"
}
out = call("POST", "/estimate", payload)
print(out["data"]["hold_credits"], out["data"]["model"])

const TOKEN = "YOUR_TOKEN";   // from /tokens.html
const BASE  = "https://api.skillsafe.ai/v1/app-api";

async function call(method, path, payload) {
  const res = await fetch(BASE + path, {
    method,
    headers: {
      "Authorization": `Bearer ${TOKEN}`,
      "Content-Type": "application/json"
    },
    body: payload === undefined ? undefined : JSON.stringify(payload)
  });
  const json = await res.json();
  if (!res.ok || !json.ok) throw new Error(json.error?.message || res.statusText);
  return json.data;
}

const payload = {
  "task": "audit",
  "sheet": "<CANVAS, DPR, CAMERA, DEPTH and OBJECTS/LIGHTS blocks; the grammar is in /llms.txt>",
  "worry": "it graded fine last time and this one will not come clean",
  "rules": "<the working rules for this lane, sent by the app>"
};
const data = await call("POST", "/estimate", payload);
console.log(data.hold_credits, data.model, data.model_alias);

package main

import (
	"bytes"
	"fmt"
	"io"
	"net/http"
)

const base = "https://api.skillsafe.ai/v1/app-api"
const token = "YOUR_TOKEN" // from /tokens.html

func main() {
	payload := []byte(`{
  "task": "audit",
  "sheet": "<CANVAS, DPR, CAMERA, DEPTH and OBJECTS/LIGHTS blocks; the grammar is in /llms.txt>",
  "worry": "it graded fine last time and this one will not come clean",
  "rules": "<the working rules for this lane, sent by the app>"
}`)
	req, _ := http.NewRequest("POST", base+"/estimate", bytes.NewReader(payload))
	req.Header.Set("Authorization", "Bearer "+token)
	req.Header.Set("Content-Type", "application/json")
	res, err := http.DefaultClient.Do(req)
	if err != nil {
		panic(err)
	}
	defer res.Body.Close()
	out, _ := io.ReadAll(res.Body)
	fmt.Println(string(out))
}

import java.net.URI;
import java.net.http.*;

public class Main {
    static final String BASE  = "https://api.skillsafe.ai/v1/app-api";
    static final String TOKEN = "YOUR_TOKEN"; // from /tokens.html

    public static void main(String[] args) throws Exception {
        String payload = """
{
  "task": "audit",
  "sheet": "<CANVAS, DPR, CAMERA, DEPTH and OBJECTS/LIGHTS blocks; the grammar is in /llms.txt>",
  "worry": "it graded fine last time and this one will not come clean",
  "rules": "<the working rules for this lane, sent by the app>"
}
""";
        HttpRequest req = HttpRequest.newBuilder()
            .uri(URI.create(BASE + "/estimate"))
            .header("Authorization", "Bearer " + TOKEN)
            .header("Content-Type", "application/json")
            .method("POST", HttpRequest.BodyPublishers.ofString(payload))
            .build();
        HttpResponse<String> res = HttpClient.newHttpClient()
            .send(req, HttpResponse.BodyHandlers.ofString());
        System.out.println(res.body());
    }
}

require 'net/http'
require 'json'
require 'uri'

BASE  = "https://api.skillsafe.ai/v1/app-api"
TOKEN = "YOUR_TOKEN" # from /tokens.html

payload = {
  "task": "audit",
  "sheet": "<CANVAS, DPR, CAMERA, DEPTH and OBJECTS/LIGHTS blocks; the grammar is in /llms.txt>",
  "worry": "it graded fine last time and this one will not come clean",
  "rules": "<the working rules for this lane, sent by the app>"
}

uri = URI("#{BASE}/estimate")
req = Net::HTTP::Post.new(uri)
req["Authorization"] = "Bearer #{TOKEN}"
req["Content-Type"] = "application/json"
req.body = JSON.dump(payload)
res = Net::HTTP.start(uri.hostname, uri.port, use_ssl: true) { |h| h.request(req) }
puts JSON.pretty_generate(JSON.parse(res.body)["data"])

<?php
$base  = "https://api.skillsafe.ai/v1/app-api";
$token = "YOUR_TOKEN"; // from /tokens.html

$payload = json_encode([
  "task" => "check",
  "sheet" => "<CANVAS, DPR, CAMERA, DEPTH and OBJECTS/LIGHTS blocks; the grammar is in /llms.txt>",
  "worry" => "it graded fine last time and this one will not come clean",
  "rules" => "<the working rules for this lane, sent by the app>"
]);

$opts = ["http" => [
    "method"  => "POST",
    "header"  => "Authorization: Bearer $token\r\nContent-Type: application/json\r\n",
    "content" => $payload,
]];
$res  = file_get_contents($base . "/estimate", false, stream_context_create($opts));
$json = json_decode($res, true);
print_r($json["data"]);

using System.Net.Http;
using System.Text;

const string Base  = "https://api.skillsafe.ai/v1/app-api";
const string Token = "YOUR_TOKEN"; // from /tokens.html

var http = new HttpClient();
http.DefaultRequestHeaders.Add("Authorization", $"Bearer {Token}");

var payload = """
{
  "task": "audit",
  "sheet": "<CANVAS, DPR, CAMERA, DEPTH and OBJECTS/LIGHTS blocks; the grammar is in /llms.txt>",
  "worry": "it graded fine last time and this one will not come clean",
  "rules": "<the working rules for this lane, sent by the app>"
}
""";
var content = new StringContent(payload, Encoding.UTF8, "application/json");
var res = await http.SendAsync(new HttpRequestMessage(new HttpMethod("POST"), Base + "/estimate")
{
    Content = content
});
Console.WriteLine(await res.Content.ReadAsStringAsync());

4. Write a package

POST /run submits the job. Always send an Idempotency-Key: a network blip that replays the same request must not bill twice. A replay with the same key returns the stored result and is not charged again; a replay with the same key but a different body is a 409.

The response carries output.output (the Markdown package), charged_credits and truncated. If truncated is true the balance sat between min_credits and hold_credits and the output was cut short - render what arrived and say so rather than presenting it as complete.

curl -sS -X POST "https://api.skillsafe.ai/v1/app-api/run" \
  -H "Authorization: Bearer $SKILLSAFE_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
  "task": "audit",
  "sheet": "<CANVAS, DPR, CAMERA, DEPTH and OBJECTS/LIGHTS blocks; the grammar is in /llms.txt>",
  "worry": "it graded fine last time and this one will not come clean",
  "rules": "<the working rules for this lane, sent by the app>"
}'

import json, urllib.request

TOKEN = "YOUR_TOKEN"   # from /tokens.html
BASE  = "https://api.skillsafe.ai/v1/app-api"

def call(method, path, payload=None, headers=None):
    data = json.dumps(payload).encode() if payload is not None else None
    req = urllib.request.Request(BASE + path, data=data, method=method)
    req.add_header("Authorization", "Bearer " + TOKEN)
    req.add_header("Content-Type", "application/json")
    req.add_header("Accept", "application/json")
    # A plain urllib request with no User-Agent is refused with 403.
    req.add_header("User-Agent", "frustum-desk-client/1.0")
    for k, v in (headers or {}).items():
        req.add_header(k, v)
    with urllib.request.urlopen(req) as r:
        return json.loads(r.read())

payload = {
  "task": "audit",
  "sheet": "<CANVAS, DPR, CAMERA, DEPTH and OBJECTS/LIGHTS blocks; the grammar is in /llms.txt>",
  "worry": "it graded fine last time and this one will not come clean",
  "rules": "<the working rules for this lane, sent by the app>"
}
out = call("POST", "/run", payload)
print(out["data"]["output"]["output"])

const TOKEN = "YOUR_TOKEN";   // from /tokens.html
const BASE  = "https://api.skillsafe.ai/v1/app-api";

async function call(method, path, payload) {
  const res = await fetch(BASE + path, {
    method,
    headers: {
      "Authorization": `Bearer ${TOKEN}`,
      "Content-Type": "application/json"
    },
    body: payload === undefined ? undefined : JSON.stringify(payload)
  });
  const json = await res.json();
  if (!res.ok || !json.ok) throw new Error(json.error?.message || res.statusText);
  return json.data;
}

const payload = {
  "task": "audit",
  "sheet": "<CANVAS, DPR, CAMERA, DEPTH and OBJECTS/LIGHTS blocks; the grammar is in /llms.txt>",
  "worry": "it graded fine last time and this one will not come clean",
  "rules": "<the working rules for this lane, sent by the app>"
};
const data = await call("POST", "/run", payload);
console.log(data.output.output);

package main

import (
	"bytes"
	"fmt"
	"io"
	"net/http"
)

const base = "https://api.skillsafe.ai/v1/app-api"
const token = "YOUR_TOKEN" // from /tokens.html

func main() {
	payload := []byte(`{
  "task": "audit",
  "sheet": "<CANVAS, DPR, CAMERA, DEPTH and OBJECTS/LIGHTS blocks; the grammar is in /llms.txt>",
  "worry": "it graded fine last time and this one will not come clean",
  "rules": "<the working rules for this lane, sent by the app>"
}`)
	req, _ := http.NewRequest("POST", base+"/run", bytes.NewReader(payload))
	req.Header.Set("Authorization", "Bearer "+token)
	req.Header.Set("Content-Type", "application/json")
	res, err := http.DefaultClient.Do(req)
	if err != nil {
		panic(err)
	}
	defer res.Body.Close()
	out, _ := io.ReadAll(res.Body)
	fmt.Println(string(out))
}

import java.net.URI;
import java.net.http.*;

public class Main {
    static final String BASE  = "https://api.skillsafe.ai/v1/app-api";
    static final String TOKEN = "YOUR_TOKEN"; // from /tokens.html

    public static void main(String[] args) throws Exception {
        String payload = """
{
  "task": "audit",
  "sheet": "<CANVAS, DPR, CAMERA, DEPTH and OBJECTS/LIGHTS blocks; the grammar is in /llms.txt>",
  "worry": "it graded fine last time and this one will not come clean",
  "rules": "<the working rules for this lane, sent by the app>"
}
""";
        HttpRequest req = HttpRequest.newBuilder()
            .uri(URI.create(BASE + "/run"))
            .header("Authorization", "Bearer " + TOKEN)
            .header("Content-Type", "application/json")
            .method("POST", HttpRequest.BodyPublishers.ofString(payload))
            .build();
        HttpResponse<String> res = HttpClient.newHttpClient()
            .send(req, HttpResponse.BodyHandlers.ofString());
        System.out.println(res.body());
    }
}

require 'net/http'
require 'json'
require 'uri'

BASE  = "https://api.skillsafe.ai/v1/app-api"
TOKEN = "YOUR_TOKEN" # from /tokens.html

payload = {
  "task": "audit",
  "sheet": "<CANVAS, DPR, CAMERA, DEPTH and OBJECTS/LIGHTS blocks; the grammar is in /llms.txt>",
  "worry": "it graded fine last time and this one will not come clean",
  "rules": "<the working rules for this lane, sent by the app>"
}

uri = URI("#{BASE}/run")
req = Net::HTTP::Post.new(uri)
req["Authorization"] = "Bearer #{TOKEN}"
req["Content-Type"] = "application/json"
req.body = JSON.dump(payload)
res = Net::HTTP.start(uri.hostname, uri.port, use_ssl: true) { |h| h.request(req) }
puts JSON.pretty_generate(JSON.parse(res.body)["data"])

<?php
$base  = "https://api.skillsafe.ai/v1/app-api";
$token = "YOUR_TOKEN"; // from /tokens.html

$payload = json_encode([
  "task" => "check",
  "sheet" => "<CANVAS, DPR, CAMERA, DEPTH and OBJECTS/LIGHTS blocks; the grammar is in /llms.txt>",
  "worry" => "it graded fine last time and this one will not come clean",
  "rules" => "<the working rules for this lane, sent by the app>"
]);

$opts = ["http" => [
    "method"  => "POST",
    "header"  => "Authorization: Bearer $token\r\nContent-Type: application/json\r\n",
    "content" => $payload,
]];
$res  = file_get_contents($base . "/run", false, stream_context_create($opts));
$json = json_decode($res, true);
print_r($json["data"]);

using System.Net.Http;
using System.Text;

const string Base  = "https://api.skillsafe.ai/v1/app-api";
const string Token = "YOUR_TOKEN"; // from /tokens.html

var http = new HttpClient();
http.DefaultRequestHeaders.Add("Authorization", $"Bearer {Token}");

var payload = """
{
  "task": "audit",
  "sheet": "<CANVAS, DPR, CAMERA, DEPTH and OBJECTS/LIGHTS blocks; the grammar is in /llms.txt>",
  "worry": "it graded fine last time and this one will not come clean",
  "rules": "<the working rules for this lane, sent by the app>"
}
""";
var content = new StringContent(payload, Encoding.UTF8, "application/json");
var res = await http.SendAsync(new HttpRequestMessage(new HttpMethod("POST"), Base + "/run")
{
    Content = content
});
Console.WriteLine(await res.Content.ReadAsStringAsync());

5. Stream a run

POST /run-stream is the same call with a text/event-stream response. Worth knowing before you build on it: from a server or from cURL you get event: delta frames carrying the output token by token; from a browser you get event: tick heartbeats and then one event: done with the whole output. Handle both, and treat ticks as liveness rather than progress.

Frame types are job (the job id), delta ({"text": "..."}), tick ({"t": seconds}), done, and error. An idempotent replay returns plain JSON with no stream at all, so check the content type before you start reading frames.

curl -sS -N -X POST "https://api.skillsafe.ai/v1/app-api/run-stream" \
  -H "Authorization: Bearer $SKILLSAFE_TOKEN" \
  -H "Content-Type: application/json" \
  -H "Accept: text/event-stream" \
  -H "Idempotency-Key: cbd-$(date +%s)" \
  -d '{
  "task": "audit",
  "sheet": "<CANVAS, DPR, CAMERA, DEPTH and OBJECTS/LIGHTS blocks; the grammar is in /llms.txt>",
  "worry": "it graded fine last time and this one will not come clean",
  "rules": "<the working rules for this lane, sent by the app>"
}'

import json, urllib.request

TOKEN = "YOUR_TOKEN"
BASE  = "https://api.skillsafe.ai/v1/app-api"

payload = {
  "task": "audit",
  "sheet": "<CANVAS, DPR, CAMERA, DEPTH and OBJECTS/LIGHTS blocks; the grammar is in /llms.txt>",
  "worry": "it graded fine last time and this one will not come clean",
  "rules": "<the working rules for this lane, sent by the app>"
}

req = urllib.request.Request(BASE + "/run-stream", data=json.dumps(payload).encode(), method="POST")
req.add_header("Authorization", "Bearer " + TOKEN)
req.add_header("Content-Type", "application/json")
req.add_header("Accept", "text/event-stream")
req.add_header("Idempotency-Key", "cbd-demo-1")
req.add_header("User-Agent", "frustum-desk-client/1.0")

event, data = "message", ""
with urllib.request.urlopen(req) as r:
    for raw in r:
        line = raw.decode().rstrip("\n")
        if line.startswith("event:"):
            event = line[6:].strip()
        elif line.startswith("data:"):
            data += line[5:].strip()
        elif line == "":
            if data:
                frame = json.loads(data)
                if event == "delta":
                    print(frame.get("text", ""), end="")
                elif event == "done":
                    print("\n--- charged:", frame.get("charged_credits"))
            event, data = "message", ""

const TOKEN = "YOUR_TOKEN";
const BASE  = "https://api.skillsafe.ai/v1/app-api";

const payload = {
  "task": "audit",
  "sheet": "<CANVAS, DPR, CAMERA, DEPTH and OBJECTS/LIGHTS blocks; the grammar is in /llms.txt>",
  "worry": "it graded fine last time and this one will not come clean",
  "rules": "<the working rules for this lane, sent by the app>"
};

const res = await fetch(BASE + "/run-stream", {
  method: "POST",
  headers: {
    "Authorization": `Bearer ${TOKEN}`,
    "Content-Type": "application/json",
    "Idempotency-Key": "cbd-demo-1"
  },
  body: JSON.stringify(payload)
});

// An idempotent replay comes back as plain JSON with no stream at all.
if (!(res.headers.get("content-type") || "").includes("text/event-stream")) {
  const json = await res.json();
  console.log(json.data.output.output);
} else {
  const reader = res.body.getReader();
  const dec = new TextDecoder();
  let buf = "";
  for (;;) {
    const { done, value } = await reader.read();
    if (done) break;
    buf += dec.decode(value, { stream: true });
    let i;
    while ((i = buf.indexOf("\n\n")) >= 0) {
      const frame = buf.slice(0, i);
      buf = buf.slice(i + 2);
      let name = "message", data = "";
      for (const line of frame.split("\n")) {
        if (line.startsWith("event:")) name = line.slice(6).trim();
        else if (line.startsWith("data:")) data += line.slice(5).trim();
      }
      if (!data) continue;
      const p = JSON.parse(data);
      if (name === "delta") process.stdout.write(p.text || "");
      if (name === "tick") console.error("still writing:", p.t + "s");
      if (name === "done") console.log("\ncharged:", p.charged_credits);
    }
  }
}

package main

import (
	"bytes"
	"fmt"
	"io"
	"net/http"
)

const base = "https://api.skillsafe.ai/v1/app-api"
const token = "YOUR_TOKEN" // from /tokens.html

func main() {
	payload := []byte(`{
  "task": "audit",
  "sheet": "<CANVAS, DPR, CAMERA, DEPTH and OBJECTS/LIGHTS blocks; the grammar is in /llms.txt>",
  "worry": "it graded fine last time and this one will not come clean",
  "rules": "<the working rules for this lane, sent by the app>"
}`)
	req, _ := http.NewRequest("POST", base+"/run-stream", bytes.NewReader(payload))
	req.Header.Set("Authorization", "Bearer "+token)
	req.Header.Set("Content-Type", "application/json")
	res, err := http.DefaultClient.Do(req)
	if err != nil {
		panic(err)
	}
	defer res.Body.Close()
	out, _ := io.ReadAll(res.Body)
	fmt.Println(string(out))
}

import java.net.URI;
import java.net.http.*;

public class Main {
    static final String BASE  = "https://api.skillsafe.ai/v1/app-api";
    static final String TOKEN = "YOUR_TOKEN"; // from /tokens.html

    public static void main(String[] args) throws Exception {
        String payload = """
{
  "task": "audit",
  "sheet": "<CANVAS, DPR, CAMERA, DEPTH and OBJECTS/LIGHTS blocks; the grammar is in /llms.txt>",
  "worry": "it graded fine last time and this one will not come clean",
  "rules": "<the working rules for this lane, sent by the app>"
}
""";
        HttpRequest req = HttpRequest.newBuilder()
            .uri(URI.create(BASE + "/run-stream"))
            .header("Authorization", "Bearer " + TOKEN)
            .header("Content-Type", "application/json")
            .method("POST", HttpRequest.BodyPublishers.ofString(payload))
            .build();
        HttpResponse<String> res = HttpClient.newHttpClient()
            .send(req, HttpResponse.BodyHandlers.ofString());
        System.out.println(res.body());
    }
}

require 'net/http'
require 'json'
require 'uri'

BASE  = "https://api.skillsafe.ai/v1/app-api"
TOKEN = "YOUR_TOKEN" # from /tokens.html

payload = {
  "task": "audit",
  "sheet": "<CANVAS, DPR, CAMERA, DEPTH and OBJECTS/LIGHTS blocks; the grammar is in /llms.txt>",
  "worry": "it graded fine last time and this one will not come clean",
  "rules": "<the working rules for this lane, sent by the app>"
}

uri = URI("#{BASE}/run-stream")
req = Net::HTTP::Post.new(uri)
req["Authorization"] = "Bearer #{TOKEN}"
req["Content-Type"] = "application/json"
req.body = JSON.dump(payload)
res = Net::HTTP.start(uri.hostname, uri.port, use_ssl: true) { |h| h.request(req) }
puts JSON.pretty_generate(JSON.parse(res.body)["data"])

<?php
$base  = "https://api.skillsafe.ai/v1/app-api";
$token = "YOUR_TOKEN"; // from /tokens.html

$payload = json_encode([
  "task" => "check",
  "sheet" => "<CANVAS, DPR, CAMERA, DEPTH and OBJECTS/LIGHTS blocks; the grammar is in /llms.txt>",
  "worry" => "it graded fine last time and this one will not come clean",
  "rules" => "<the working rules for this lane, sent by the app>"
]);

$opts = ["http" => [
    "method"  => "POST",
    "header"  => "Authorization: Bearer $token\r\nContent-Type: application/json\r\n",
    "content" => $payload,
]];
$res  = file_get_contents($base . "/run-stream", false, stream_context_create($opts));
$json = json_decode($res, true);
print_r($json["data"]);

using System.Net.Http;
using System.Text;

const string Base  = "https://api.skillsafe.ai/v1/app-api";
const string Token = "YOUR_TOKEN"; // from /tokens.html

var http = new HttpClient();
http.DefaultRequestHeaders.Add("Authorization", $"Bearer {Token}");

var payload = """
{
  "task": "audit",
  "sheet": "<CANVAS, DPR, CAMERA, DEPTH and OBJECTS/LIGHTS blocks; the grammar is in /llms.txt>",
  "worry": "it graded fine last time and this one will not come clean",
  "rules": "<the working rules for this lane, sent by the app>"
}
""";
var content = new StringContent(payload, Encoding.UTF8, "application/json");
var res = await http.SendAsync(new HttpRequestMessage(new HttpMethod("POST"), Base + "/run-stream")
{
    Content = content
});
Console.WriteLine(await res.Content.ReadAsStringAsync());

6. Read the result

output.output is Markdown in the envelope this app's system prompt guarantees: every section is a level-two heading spelled exactly as listed in the lane table above, in that order; tables are GitHub pipe tables with the declared columns; prompts are in fenced blocks opened with three backticks and the word text; checklists are - [x] lines.

So parsing is a split on /^## / - but do it fence-aware, because a prompt block can legitimately contain a line starting with ##. Count the sections you got against the ones the lane declares: a short list means the run was truncated, not that the contract changed.

def sections(md):
    out, name, buf, fence = {}, None, [], False
    for line in md.split("\n"):
        if line.lstrip().startswith("```"):
            fence = not fence
        if not fence and line.startswith("## "):
            if name:
                out[name] = "\n".join(buf).strip()
            name, buf = line[3:].strip(), []
            continue
        if name:
            buf.append(line)
    if name:
        out[name] = "\n".join(buf).strip()
    return out

The artifact most callers want is the fenced text block inside ## The Sheet or ## Corrected Sheet - that is a complete sheet in the grammar above, so it can be fed straight back into another lane with nothing carried alongside it. Every other section is prose and tables meant to be read.

Rate limits and good manners

/estimate and /me are free. Call them as much as you like, within reason.
A 429 means back off with a delay, not retry immediately.
Send an Idempotency-Key on every /run. Derive it from a hash of the body plus an attempt counter, so a retry of the same request reuses the key and a deliberate re-run gets a new one.
The engine in the web app is client-side only and has no endpoint. What it computes is published in full in llms.txt, and it is one projection plus three consequences. The horizontal field of view is 2 × atan(tan(fov÷2) × aspect), so it follows the canvas and the vertical does not move. The six frustum planes are built from the camera's position, direction, angles and planes with inward normals, and a bounding sphere is rejected when its signed distance to any plane is below −radius - which is exactly what a renderer does, and exactly why an object can be submitted while being invisible. The depth step is z² × (1/near − 1/far) ÷ (2^B − 1), because the buffer holds f/(f−n) − f·n/((f−n)·z) and that is hyperbolic in z. And a shadow map's texel density is mapSize ÷ span. So you can compute every figure this app produces in your own pipeline without it. It is arithmetic on the sheet you paste: no WebGL context is created, no frame is rendered and no GPU is measured. It is the PROJECTION and nothing else - materials, textures, batching, overdraw and shader cost all decide what a frame costs and none of them changes what the frustum contains. Every object is an axis-aligned primitive rather than your mesh, so the culling-slack figures are the shape of the answer for your mesh rather than the answer, and the error runs one way because a real mesh's sphere is at least this loose. The depth arithmetic assumes a FIXED-POINT buffer and the standard projection, which is what a browser gives you; a reversed-Z float buffer distributes precision almost uniformly and WebGL cannot express one. The shadow figures are for a DIRECTIONAL light's orthographic camera, and cascades are several second frustums this page does not model. The camera, one row per canvas with its own horizontal angle, one row per object with its bounding radius, view depth, depth step and culling verdict, and one row per light with its texel density and its own frustum are all sent with each run as prescan, and the system prompt requires answering them.