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MCP Stateless Check

MCP004 — Results are missing the required resultType field
Severity error
Fixed by Upgrading your MCP SDK to a release targeting 2026-07-28
Transports stdio, http
Specification 2026-07-28
Changelog entry Major change 8 (SEP-2322)

Why this changed

SEP-2322 added a required resultType discriminator to every result, so a client can tell an ordinary result from an interim Multi Round-Trip request. Clients are told to treat a missing field as "complete" for backward compatibility, which means omitting it is survivable today but blocks the server from ever using MRTR.

Running just this check

Terminal window
npx mcp-stateless --stdio "node dist/server.js" --only MCP004

Suppressing it

If this check does not apply to your server, skip it:

Terminal window
npx mcp-stateless --stdio "node dist/server.js" --skip MCP004

Rule ids are permanent and are never reissued, so a suppression cannot start silently matching a different check later.

Generated from src/rules/MCP004.ts by scripts/gen-rule-docs.mjs. Edit the rule source, not this page.