change(mcp): advertise protocol revision 2025-11-25, negotiate older versions#109
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…versions The Worker pinned 2025-06-18 while 2025-11-25 has been stable since November. Nothing in the new revision changes this server's feature surface (no auth, elicitation, sampling, tasks, or SSE here), so the upgrade is advertisement plus three real fixes: - initialize now does spec-correct version negotiation: echo the client's requested version when supported (2025-11-25, 2025-06-18, 2025-03-26), answer with our latest otherwise. - Tool execution errors return isError tool results instead of -32603 protocol errors (SEP-1303), so calling models can self-correct. - serverInfo gains the 2025-11-25 description, websiteUrl, and icons fields. Drift fixed along the way: the static server card claimed "96 spec pages" (there are 163) and both it and the Worker landing page were missing the get_changes tool. The mcp-and-tool-discovery page no longer describes HTTP+SSE as the remote transport (deprecated; Streamable HTTP replaced it), and both citing pages now reference the 2025-11-25 spec URL. SKILL.md revision + digest resynced via sign:skill. The next revision (draft, expected 2026-07-28) is a breaking rework (removes initialize, adds server/discover, required resultType) and is deliberately not adopted while still in draft. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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Why
The daily standards scan flagged MCP revision drift: the Worker and discovery docs pinned
2025-06-18while2025-11-25has been stable since November 2025.What changed between the revisions, and what it means for us
The 2025-11-25 changelog is almost entirely additive, and most of it (OIDC discovery, incremental scope consent, URL elicitation, sampling tools, OAuth client ID metadata, experimental tasks) touches surfaces this server does not have — it is stateless, read-only, unauthenticated, tools + prompts only. So the upgrade is cheap, but three items are real:
initializepreviously always answered2025-06-18regardless of what the client asked for. It now echoes the client's requested version when supported (2025-11-25,2025-06-18,2025-03-26— the feature surface is identical across them for this server) and answers with our latest otherwise, per the lifecycle spec.isError: truetool results instead of-32603protocol errors, so a calling model can read the message and self-correct. (The existing/admin/statserror logging already keys offresult.isError, so error rows keep flowing.)serverInfometadata: the newdescription,websiteUrl, andiconsfields, pointing at the site icon.Drift fixed along the way
get_changestool. Both now list all six tools; the card drops the hardcoded count.SKILL.mdprotocol revision + digest resynced vianpm run sign:skill.What is deliberately NOT done
The next revision (draft, expected 2026-07-28) is a breaking rework: removes the
initializehandshake, adds a mandatoryserver/discoverRPC, requiredresultTypeon results, removesping/logging/setLevel. Adopting a draft would violate our own ship-it-first honesty bar; revisit once it is stamped stable. Worth a scan watch.Verified
Ran
wrangler devand confirmed: requested2025-06-18→ echoed; requested unknown2026-07-28→ answered2025-11-25; tool throw →isErrorresult; server card and landing page listget_changes.tsc --noEmit,eslint,prettier --check, andcheck:skillall pass.No changelog entry: this is plumbing plus a citation/transport-wording touch-up on two pages — flagged as borderline in the session summary for Joost to call.
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