The c4x-validator MCP server exposes a single tool with a clear, well-defined purpose. The tool name follows verb_noun convention (validate_c4x), the description is actionable and specific (explains what it validates, that it reports errors with line/column info, and explicitly states it does NOT fix code), and the input schema is properly structured with a required 'code' parameter that has a clear description. The server demonstrates good foundation patterns: a read-only, idempotent tool with clear error semantics. However, the server lacks output schema documentation (no documented structure for success vs. error responses), lacks tool annotations (readOnlyHint would benefit from explicit marking), and has minimal protocol support (STDIO-only, no resources despite claiming resources=true in features, no progress/cancellation/sampling). The single tool design is appropriate for a validation microservice, but the output contract should be explicitly documented in the tool definition.

• Add explicit output schema documentation to the tool definition. Document the response structure for both success case (e.g., {success: true, valid: true}) and error case (e.g., {success: true, valid: false, errors: [{line: number, column: number, message: string, code: string}]}). Include field type annotations and example responses.
• Add readOnlyHint: true to the tool definition to explicitly mark this as a side-effect-free validation tool.
• Enhance the description with recovery guidance: 'When validation fails, the returned error objects include line and column numbers (1-indexed) and a descriptive message. Use these to locate and fix syntax errors in the code. Errors are categorized by type (e.g., SyntaxError, ReferenceError) to help guide corrections.'
• Consider documenting example C4X code snippets (valid and invalid) in supporting documentation external to the tool definition, so that clients have reference material without cluttering the schema.
• Document acceptable input size limits (max characters for 'code' parameter) to prevent agents from sending extremely large payloads.