API reference

The FreeTheAI API is an OpenAI-compatible HTTP API with JSON bodies. This reference covers every public endpoint. The machine-readable contract is the OpenAPI 3.1 document at api.freetheai.org/openapi.json, also listed at freetheai.org/.well-known/api-catalog.

Base URL

https://api.freetheai.org

Every path below starts with /v1. OpenAI SDKs take https://api.freetheai.org/v1 as their base URL; the Anthropic SDK takes https://api.freetheai.org. See Endpoints and base URLs.

Authentication

Send your API key on every request:

Authorization: Bearer ftai_your_key_here

x-api-key: ftai_your_key_here works too. Keys are created at Dashboard > API keys on freetheai.org; see Account and API keys. Free models also need a confirmed email and today's check-in.

Endpoints

Method and path	What it does
POST /v1/chat/completions	Create a chat completion (OpenAI Chat Completions format)
POST /v1/responses	Create a model response (OpenAI Responses format)
POST /v1/messages	Create a message (Anthropic Messages format)
GET /v1/models	List the models your key can use
POST /v1/search	Search the web
POST /v1/answer	Answer a question from the web, with sources
GET /v1/health	Service health (no key needed)

The three inference endpoints accept every free model, stream with "stream": true, and support tool calls. Fields this reference does not list are passed through to the model when it supports them, so standard OpenAI and Anthropic parameters work as you would expect.

Errors

Errors return a JSON body with an HTTP status:

{
  "error": {
    "message": "Daily check-in required for free models. Visit https://freetheai.org/checkin to solve the captcha.",
    "type": "gateway_error"
  }
}

Status	Meaning
400	The request is invalid, uses a setting the model does not accept, or was blocked by the model's content filter (error.code content_filter).
401	The API key is missing, incomplete, revoked, or expired.
402	Paid requests only (paid models are coming soon).
403	Not allowed: email not confirmed, no check-in today, a key restriction, or an account on hold.
404	Unknown model (error.code model_not_found).
413	The body is larger than 8 MB.
429	A limit was reached: one request at a time, daily free requests, a usage window, or a rate limit.
502	The model failed, or a stream broke. Carries error.error_id and the X-Error-ID header.
503	The model is busy or paused right now. Not counted against your limits.

Every message, word for word, with its fix: Errors.

Health

GEThttps://api.freetheai.org/v1/health

Reports whether the API is reachable. It needs no key.

curl https://api.freetheai.org/v1/health

{ "status": "ok" }

For the status of each model, see the status page.

Conventions

• JSON in, JSON out. Send Content-Type: application/json. Streams are text/event-stream.
• Model IDs are case-sensitive and start with fta/. Copy them from the Models page or GET /v1/models.
• Usage is reported in every response's usage object, and in the final chunk of a stream.
• Privacy. FreeTheAI does not store prompts or replies.