Echo MCP defines 3 tools with clear verb-noun naming (list_schemas, get_schema, echo) and proper Zod schemas. All tools have descriptions (10-100 chars) and input parameters are typed. Tool annotations (readOnlyHint, destructiveHint, openWorldHint) are present. However, descriptions are minimal (34-100 chars, below the 50-200 char LLM-optimized baseline), parameter descriptions lack context about expected formats/constraints, and output schemas are not documented. The 'echo' tool's 'payload' parameter uses z.unknown() without validation guidance, and error handling is absent from visible code.

• Expand tool descriptions to 50-200 characters. Example: 'echo' → 'Validate a JSON payload against a registered schema and return it in a stable envelope. Use this to ensure structured data conforms to expected types before downstream processing. Returns {valid: bool, payload: object, errors: string[]}.'
• Document output schemas explicitly. Add JSDoc or inline comments showing return types: list_schemas returns {schemas: {id: string, name: string}[]}, get_schema returns {id: string, schema: object}, echo returns {valid: boolean, payload: unknown, errors: string[]}.
• Add parameter constraints to descriptions. E.g., 'schema_id: string (1-255 chars, alphanumeric + underscore, case-sensitive)' and 'payload: any JSON-serializable value (max 10MB)'.
• Implement and document error handling. Catch validation failures in echo() and return {valid: false, errors: ['Field X must be string', 'Field Y is required']} with actionable messages.
• Document session behavior in tool descriptions. Clarify: 'Uses the current MCP session ID to scope schemas. If no session is active, defaults to local-session.' This helps LLMs understand multi-user vs single-user contexts.