Fix: an unsupported protocol version is rejected -32022 with data.supported
Web-audit fix skill for the
mcp-modern-version-rejectcheck (MCP, SHOULD).
Goal
Refuse unsupported protocol version claims with -32022 and advertise the served revisions.
Fix
Reject a request claiming an unsupported MCP-Protocol-Version with error.code: -32022 (UnsupportedProtocolVersion) and populate error.data.supported with the revisions you serve (for example ["2026-07-28"]); echoing the claim in error.data.requested helps debugging. The data.supported array is what lets a typed client fall back to a revision you both speak, so an envelope without it fails the check.
Resources
Copy-paste prompt
Paste this into your coding agent. Your audit adds what it observed for this check:
Verify
Re-run the audit at https://anc.dev/audit or call the audit_website MCP tool; the mcp-modern-version-reject check should report pass.