SEC-001: Tool schemas do not depend on a network $ref

Severity	Applies to	Spec section
warn	both eras, stdio, http	2026-07-28/basic/index#ref-resolution

Scans every tool's inputSchema and outputSchema for a $ref that points outside the schema (an http(s) or other absolute URI). Implementations MUST NOT automatically dereference $ref values that resolve to a network URI, and schemas that fail to validate because of an unresolved external $ref SHOULD be rejected, so a client cannot validate arguments or results for such a tool. MCPProbe cannot observe whether the server itself fetches remote $refs (no MCP message sends the server a schema to validate), so this check covers the half that is visible: the server's own published schemas. Inline the referenced definitions under $defs instead. Runs once per server.

From the command line: mcpprobe checks explain SEC-001. To leave it out of a run, add "SEC-001" to [checks] disable in mcpprobe.toml; to change how much it counts, use severity_overrides.