CONF-008: Unknown tools get a JSON-RPC error, not a tool result¶
| Severity | Applies to | Spec section |
|---|---|---|
| info | both eras, stdio, http | 2026-07-28/server/tools#error-handling |
Calls a tool name that is not in tools/list (checked first, so no real tool is ever called). The spec's error-handling section lists an unknown tool as a protocol error, returned as a standard JSON-RPC error, as opposed to tool execution errors reported with isError: true. The section has no MUST or SHOULD, so this is info and never fails a run. Any JSON-RPC error code passes; the spec's example uses -32602. The 2025-11-25 tools page lists unknown tools as a protocol error too. On servers that speak both eras it runs twice: once with modern requests, and once inside a legacy initialize session as
From the command line: mcpprobe checks explain CONF-008. To leave it out of a run, add "CONF-008" to [checks] disable in mcpprobe.toml; to change how much it counts, use severity_overrides.