Driving Kelvin 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 Choose the balance, then solve the gels brief, known Summary, The Sheet, The Setting, Reasoning, Next Step

check What every source lands at, and what the mix is sheet, worry Summary, Verdict, Findings, Corrected Sheet, Next Step

mix What the sources really mix to sheet Summary, What Each Source Contributes, Mired Against Kelvin, The Spread, Next Step

gels Which gel each source actually needs sheet Summary, Every Source, What Each Gel Is Worth Here, Where Nothing Fits, Next Step

deliver Decide what changes: the balance, the gels, or the fixtures sheet, fixed Summary, Moving The Balance Fixes, Only A Gel Or A Fixture Fixes, Nothing Fixes, Next Step

task	Lane	Fields	Sections returned
`plan`	Choose the balance, then solve the gels	`brief, known`	Summary, The Sheet, The Setting, Reasoning, Next Step
`check`	What every source lands at, and what the mix is	`sheet, worry`	Summary, Verdict, Findings, Corrected Sheet, Next Step
`mix`	What the sources really mix to	`sheet`	Summary, What Each Source Contributes, Mired Against Kelvin, The Spread, Next Step
`gels`	Which gel each source actually needs	`sheet`	Summary, Every Source, What Each Gel Is Worth Here, Where Nothing Fits, Next Step
`deliver`	Decide what changes: the balance, the gels, or the fixtures	`sheet, fixed`	Summary, Moving The Balance Fixes, Only A Gel Or A Fixture Fixes, Nothing Fixes, Next Step

Only task and the lane's own required fields are mandatory: sheet on check, mix, gels and deliver; brief on plan. Every field is a string - there are no number fields on this app. The sheet is two blocks, SETUP and SOURCES, and the grammar is in /llms.txt and in the free panel on the app itself.

A SOURCES row is id | what it is | kelvin | level | gel | why. A temperature accepts 5600, 5600K or 5.6k. The level is a weight, not a measurement - it decides how much each source counts toward the mix, so any consistent unit works and the absolute values cancel.

The gel column accepts a name (none, quarter cto, half ctb, full cto, double cto), a Lee number (Lee 204), or an explicit shift (+42 mired) for a fixture whose own temperature is being changed rather than filtered. Several sources can carry the same gel and each is computed from its own starting point, which is the whole point: a gel is a constant shift in mireds and therefore a variable one in Kelvin.

SETUP takes name, balance, target and tolerance. balance is what the camera is set to, and balance | mix is the shorthand for "whatever the camera would auto-balance to" - it makes the sheet report how far each source sits from the average rather than from a number somebody chose. tolerance is the residual cast you will accept, in mireds; it defaults to 5, which is about the smallest difference visible side by side on a white card. Leaving the balance out entirely is reported as a warning, because every cast on the page is measured from it.

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 check and split lanes rather than shorten them - a findings table, a corrected sheet and two ranked tables 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", "kelvin-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": "check",
  "sheet": "<a SETUP block and a SOURCES block - 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", "kelvin-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": "check",
  "sheet": "<a SETUP block and a SOURCES block - 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": "check",
  "sheet": "<a SETUP block and a SOURCES block - 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": "check",
  "sheet": "<a SETUP block and a SOURCES block - 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": "check",
  "sheet": "<a SETUP block and a SOURCES block - 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": "check",
  "sheet": "<a SETUP block and a SOURCES block - 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" => "<a SETUP block and a SOURCES block - 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": "check",
  "sheet": "<a SETUP block and a SOURCES block - 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": "check",
  "sheet": "<a SETUP block and a SOURCES block - 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", "kelvin-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": "check",
  "sheet": "<a SETUP block and a SOURCES block - 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": "check",
  "sheet": "<a SETUP block and a SOURCES block - 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": "check",
  "sheet": "<a SETUP block and a SOURCES block - 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": "check",
  "sheet": "<a SETUP block and a SOURCES block - 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": "check",
  "sheet": "<a SETUP block and a SOURCES block - 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" => "<a SETUP block and a SOURCES block - 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": "check",
  "sheet": "<a SETUP block and a SOURCES block - 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": "check",
  "sheet": "<a SETUP block and a SOURCES block - 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": "check",
  "sheet": "<a SETUP block and a SOURCES block - 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", "kelvin-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": "check",
  "sheet": "<a SETUP block and a SOURCES block - 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": "check",
  "sheet": "<a SETUP block and a SOURCES block - 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": "check",
  "sheet": "<a SETUP block and a SOURCES block - 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": "check",
  "sheet": "<a SETUP block and a SOURCES block - 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" => "<a SETUP block and a SOURCES block - 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": "check",
  "sheet": "<a SETUP block and a SOURCES block - 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 - a mired is 1,000,000 / K, a gel is a constant mired shift so a gelled source is mired(source) + shift, the correction a source needs is mired(balance) - mired(source), the mix is a level-weighted average of the MIREDS, and the spread is the widest gap between any two sources in mireds - so you can compute every figure this app produces in your own pipeline without it. It is arithmetic on the numbers you type: it has metered nothing, it only knows the blue-to-orange axis and not green-to-magenta, it assumes sources close to a blackbody, the mired average is the industry approximation rather than exact chromaticity, and gel values differ between manufacturers by a few mireds. Every source's landing point and residual, the mix, what a Kelvin average would have said, the spread and the nearest standard gel for each correction are all sent with every run as prescan, and the system prompt requires answering them.