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The StefanBrain developer platform gives your code and AI assistants access to the StefanBrain agent and its supported developer tools. An active StefanBrain plan or trial is required. Create an API key in Settings → Developers, then choose the surface that matches your task.

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Choose between REST and MCP

  • MCP is for a person working interactively inside an AI assistant. For standard member accounts, MCP usage bills the plan’s monthly pool.
  • REST is for integrations, pipelines, and automated traffic. A stefan_sk_... key bills the prepaid API wallet. A stefan_oat_... OAuth token bills the plan pool.
Contracted partner accounts can route plan-pool traffic to the wallet or use other account-specific terms. Use the billing lane reported for that account. Agent Runs are the primary REST surface. The agent plans the work, selects tools, and returns its final response in output. Use direct tools when your application needs one specific capability or a raw result.

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Important behavior

  • Runs accept file attachments through multipart/form-data.
  • Run attachments accept documents and images, not audio or video files. Put a hosted video URL in message instead.
  • Runs can constrain their final response to a JSON schema through output_config.
  • A REST API turn returns its full assistant response in output; it does not write that response into an in-app canvas document.
  • There is no model selector. Agent Runs execute the model that operates the StefanBrain product.
  • Keep the chat identifier from a response and reuse it for follow-up turns in the same conversation.
  • Fetch the live Tools or MCP catalog before relying on a tool name. Availability can depend on your access and the current deployment.

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Start building

Send your first request

Create a key and start a synchronous Agent Run.

Connect through MCP

Add StefanBrain to Codex, Claude, ChatGPT, Cursor, or another MCP client.

Call tools and jobs

Discover live tool schemas and handle long-running work.

Stage and download files

Attach local files to asks or retrieve current workspace files from a chat.

Read Meta video transcripts

Reuse stored transcripts or request one for an accessible Meta video.

Use the TypeScript SDK

Add typed asks, runs, tools, jobs, and files to a Node.js application.

Use the CLI

Run and script StefanBrain from a shell with stable JSON output.

Run parallel agent sessions

Give concurrent forks shared project context and separate chats.

Give the docs to an agent

Use Markdown and OpenAPI sources instead of scraping HTML.

Send agent feedback

Report a failing call or a missing capability, and read the team’s reply.