AI Engineering from Scratch（英文原版）

Given a sequence of MCP JSON-RPC envelopes, audit each message independently against MCP 2026-07-28. Detect legacy traffic, but never assume a handshake or protocol session exists.

Produce:

1. Message annotation. State direction, JSON-RPC kind, method, primitive, request id, and detected era.
2. Modern metadata check. For every request, verify params._meta.io.modelcontextprotocol/protocolVersion and params._meta.io.modelcontextprotocol/clientCapabilities. Record whether recommended clientInfo is present.
3. Result check. Verify every modern success has resultType: "complete" or another specified result type, plus recommended server identity in result _meta.
4. Discovery and version check. Verify modern servers implement server/discover. Interpret -32022 as modern evidence and check data.requested plus data.supported.
5. Cache check. For server/discover, list methods, and resources/read, require ttlMs and cacheScope. Flag nondeterministic list ordering.
6. Direction check. Reject server-initiated JSON-RPC requests in modern traffic. Allow request-related notifications and client-opened subscriptions/listen streams.
7. Compatibility check. Label initialize and notifications/initialized as legacy only. Do not require them in modern traffic.

Hard rejects:

• Treating a stdio process, HTTP connection, or Mcp-Session-Id as modern protocol state.
• Inferring client capabilities from an earlier request.
• Falling back to legacy after a recognized modern error such as -32020, -32021, or -32022.
• Accepting a modern success without resultType.

Refusal rules:

• If the transcript is not JSON-RPC 2.0, stop and identify the incompatible envelope.
• If asked to silently rewrite evidence, refuse. Preserve the original transcript and produce a separate corrected example.

Output one line per message in arrival order:

[request/modern/tools] id=7 tools/list metadata=valid

End with counts for modern, legacy, invalid, and ambiguous messages, followed by the first corrective action.