Call the Flatkey API directly

Base URL: https://router.flatkey.ai Flatkey exposes an OpenAI-compatible REST API. If you already have an HTTP client, you do not need an SDK. This page is the shortest path from a key to a working request.

Authenticate

Every request carries your key as a bearer token:

Authorization: Bearer YOUR_FLATKEY_API_KEY

Create a key in the console. Keys start with sk-fk-. Store it in an environment variable and keep it out of source control and browser code.

export FLATKEY_API_KEY="sk-fk-..."

Send a request

curl --fail-with-body -sS https://router.flatkey.ai/v1/chat/completions \
  -H "Authorization: Bearer $FLATKEY_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "claude-sonnet-5",
    "messages": [{ "role": "user", "content": "Hello!" }]
  }'

A successful call returns the standard chat completion object with choices and usage.

Available endpoints

Endpoint	Purpose
`POST /v1/chat/completions`	Text and chat generation
`POST /v1/responses`	Responses API, for OpenAI models
`POST /v1/images/generations`	Image generation and editing
`POST /v1/videos`	Video generation, asynchronous
`GET /v1/videos/{task_id}`	Poll a video task
`GET /v1/models`	List available models
`GET /v1/credits`	Remaining balance

POST /v1/responses currently works with OpenAI models. Other families return an error on this endpoint — use POST /v1/chat/completions for them.

Check your balance

curl --fail-with-body -sS https://router.flatkey.ai/v1/credits \
  -H "Authorization: Bearer $FLATKEY_API_KEY"

{ "remaining": 34.18, "used": 185.13 }

Handle errors

Errors return a JSON body with a message you can act on:

{ "error": { "message": "No available channel for model ..." } }

Status	Meaning	What to do
`400`	Malformed request	Read the message; it names the offending field
`401`	Invalid key	Check the `Authorization` header and key value
`429`	Too many requests	Back off and retry
`500`, `503`	Model or route unavailable	Switch models. Retrying the same one rarely clears it

Full list in the error reference.

Next steps

API reference

Every endpoint, parameter, and response field.

Use an SDK instead

Keep your OpenAI or Anthropic client and change one line.

Quick Start

Code

Mainstream AI Tools

Media Generation

Popular models

Dashboard

Reference

Call the Flatkey API directly

Authenticate

Send a request

Available endpoints

Check your balance

Handle errors

Next steps

API reference

Use an SDK instead

​Authenticate

​Send a request

​Available endpoints

​Check your balance

​Handle errors

​Next steps

API reference

Use an SDK instead

Authenticate

Send a request

Available endpoints

Check your balance

Handle errors

Next steps