Tip: The Concrete MCP Migration Checklist — New Headers, `server/discover`, and a Changed Error Code

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Server authors must now support `Mcp-Method` and `Mcp-Name` headers on Streamable HTTP POSTs, implement a mandatory `server/discover` RPC advertising supported protocol versions and capabilities, read `io.modelcontextprotocol/protocolVersion` and `/clientCapabilities` from `_meta` on every request, and add `ttlMs` plus `cacheScope` to `tools/list`, `resources/list`, and `prompts/list` results (SEP-2549). Client authors must handle `InputRequiredResult` payloads instead of server-initiated reverse calls, validate the OAuth `iss` parameter per RFC 9207, and key persisted credentials by issuer. The one that will silently break you: clients matching error code `-32002` must switch to the standard JSON-RPC `-32600`.