Protocol
OpenAI MCP
OpenAI shipped MCP support into ChatGPT Apps in late 2025 and sits as a platinum member and co-founder of the Linux Foundation Agentic AI Foundation. The protocol Anthropic created in November 2024 now runs across OpenAI's surfaces alongside Claude, Cursor, Windsurf, and the rest of the agent-client ecosystem.
OpenAI's path to MCP
- June 2023 OpenAI shipped function-calling in the Chat Completions API, the proprietary precursor to standardized tool use.
- August 2025 OpenAI published AGENTS.md, a markdown standard for repository-level agent instructions.
- Late 2025 OpenAI integrated MCP into ChatGPT Apps as the standard for connecting GPT models to external tools and data.
- December 9, 2025 OpenAI co-founded the LF Agentic AI Foundation alongside Anthropic and Block; co-donated AGENTS.md as one of three founding projects.
OpenAI's seat at the AAIF puts it on a platinum tier alongside Amazon Web Services, Anthropic, Block, Bloomberg, Cloudflare, Google, and Microsoft.
MCP in ChatGPT Apps, operationally
The wire is the same: JSON-RPC 2.0 over the documented transports. The server-side primitives are the same: Resources, Tools, Prompts. The client-side capabilities are the same: Roots, Sampling, Elicitation. ChatGPT registers servers through its Apps surface; the initialize handshake runs at session start. A server built for Claude Desktop or Cursor runs in ChatGPT Apps without code changes.
Function-calling and MCP, today
Function-calling still ships in OpenAI's API for direct API consumers who want OpenAI-bound tool definitions inline with their completion requests. MCP is the route for cross-client portable tools that work on ChatGPT and Claude and Cursor and every other host that speaks the spec. The two coexist: OpenAI maintains function-calling for its API surface and ships MCP for its agent surface.