| id | example-mcp-server |
|---|---|
| type | example |
| title | Model Context Protocol (MCP) Tool Server |
| summary | Build a stateless 2026-07-28 MCP tool server with JSON-RPC 2.0 dispatch, no initialize handshake, schema validation, error isolation, and the input_required round-trip. |
| lang | en-US |
| content_version | 2 |
| status | reviewed |
| reviewed_on | 2026-09-06 |
The Model Context Protocol (MCP) connects AI models and agents to external tools and data.
The 2026-07-28 specification is stateless-first: the initialize handshake and
Mcp-Session-Id sessions were removed, requests self-describe their protocol version
through _meta, and server-initiated elicitation was replaced by a multi-round-trip
input_required flow.
A production MCP server under this specification must parse standard JSON-RPC 2.0
requests, answer tools/list and tools/call directly without any prior handshake,
validate arguments, handle execution errors gracefully, and let a tool request additional
client input through a result with resultType: "input_required" that the client
completes by retrying the same call with inputResponses.
python examples/mcp-server/verify.py starter --expect-failure python examples/mcp-server/verify.py solution
The first command reports the expected failure from the naive starter.
The second verifies the compliant solution. Give TASK.md to a coding agent,
ask it to fix only starter/mcp_server.py, and run:
python examples/mcp-server/verify.py starter
For the full migration background — what was removed, deprecated, and hardened in 2026-07-28 — read Migrate a Python MCP server to the 2026-07-28 specification.
See this example on flypython.com: the browsable contract, step-by-step walkthrough, and current review state.