only_mcp

A simple MCP v0.2 client and server implementation, for me to learn about MCP.

IT is not a complete implementation. Neither is it to be used for production.

Story So Far

Spent the weekend implementing MCP v0.2—exactly as fun as it sounds! Agents can now leverage authenticated tools, though there's room for improvement.

Key observations:

• Protocol Changes: MCP v0.2 significantly differs from v0.1—most notably, the SSE endpoint is gone. It also relies on a .well-known OAuth flow for auth. The introduction of application/json requests simplify some interactions but remove the option for server push via SSE.

• SDK and Tooling Gaps: Current Python SDK to build your MCP server quickly is still at v0.2 with limited auth support, which pushed me into building a Falcon-based server compatible with both standards. Dev tooling lags behind—Claude integration, for instance, still demands local stdio-based setups. The promising mcp-proxy tool doesn't yet support v0.2, causing unexpected detours during implementation.

• Interoperability Concerns: MCP's tool schema differs from OpenAI's chat-completion standard, complicating implementations. Function call chains (e.g., fetching schema before updates) also present challenges—tool-calling workflows could be more streamlined.

• Long-running Tasks: While direct support is still missing, MCP v0.2 introduces event IDs for task status polling—a welcome addition, though yet to be tested in my setup.

• Deployment and Strategy: MCP endpoints ideally coexist alongside REST APIs and OAuth flows, making it suitable for dedicated agent traffic handling. Cloudflare emerges as a solid managed option, though self-hosting might become preferable as tooling matures. Founders considering building a standalone MCP gateway in the cloud might want to reassess the long-term viability of that approach.

Overall, MCP v0.2 is progressing nicely but needs a few iterations for tooling and SDK maturity.

Developer Instructions

1. Pre-commit

pre-commit install

1. We only develop inside containers.

docker compose up --build

1. Frontend dependencies are managed locally. If you need to run eslint manually, run:

npm --prefix frontend install && npx eslint