x-mcp demonstrates solid tool naming (verb-first: search_*, fetch_*, list_*, resolve_*, check_*) and comprehensive descriptions (avg ~180 chars, well above 10-char minimum). All 12 tools have input schemas with typed parameters and descriptions. However, output schemas are undocumented, responses are inferred from code (e.g., fetch_ai_feeds returns {items, failures, truncated}) but not formally declared in tool definitions. Error handling is minimal: no recovery guidance, no categorization of retryable vs fatal errors, no validation error messages. Parameter constraints exist (e.g., limit clamping in fetch_ai_feeds) but are not exposed in schemas as enums or ranges. Missing: per-parameter descriptions for some optional params (e.g., languages in fetch_youtube_transcript lacks detail on format/codes). No tool annotations (readOnlyHint, destructiveHint, idempotentHint) despite all tools being read-only.

• Add explicit return type schemas to all tool definitions. E.g., fetch_ai_feeds should declare: {type: object, properties: {items: {type: array, items: {type: object, properties: {title, url, source, ...}}}, failures: {type: array}, truncated: {type: boolean}}}.
• Convert free-form string parameters to enums where valid values are known. E.g., search_reddit.since → enum: [hour, day, week, month, year, all]. search_x.query_type → enum: [Latest, Top].
• Add readOnlyHint: true to all tool definitions (via MCP 2.0 tool annotations) to signal safety to agents.
• Enhance error messages with recovery guidance. E.g., if fetch_youtube_transcript fails: 'Video not found or has no transcript. Try search_youtube() to find a valid video ID first.' If fetch_rss fails on invalid URL: 'Invalid feed URL. Use discover_feeds() to find the correct URL from a blog homepage.'
• Document output schemas in tool descriptions or add structured return type metadata. E.g., 'Returns list of {title, url, source, date, score} dicts' for search_hn.