The YouTube MCP server demonstrates moderate definition quality with consistent naming patterns and comprehensive parameter schemas. All 22 tools follow a clear verb_noun naming convention (e.g., activities_list, channels_getChannel, videos_getStatistics) that aids discoverability. Parameter schemas are well-formed with proper type definitions (string, integer, array, boolean) and descriptions. However, tool descriptions are brief (10-30 characters on average), falling below the recommended 50-200 character range for LLM optimization. Description quality varies: some tools like 'search_list' (21 chars) and 'i18nLanguages_list' (10 chars) are too terse to guide LLM selection effectively. Output schemas are not documented in the provided source, making it impossible to verify what fields agents should expect from each tool. Error handling patterns and recovery guidance are not visible in the tool definitions. The Layer 1/2/3 architecture suggests composition is partially addressed, but tool chaining requirements (ensuring output IDs match input parameters) cannot be fully assessed from the available code snippets.

• Expand all tool descriptions to 50-200 characters. For example, replace 'Public activity lookup for the documented Google Developers channel.' with 'List public activities for a YouTube channel. Use this to discover recent uploads, likes, and subscriptions. Requires a valid channelId; use channels_list to find channels by name first.'
• Document output schemas for every tool, showing field names, types, and which fields are required vs optional. For videos_getVideo, document that it returns {videoId, title, description, statistics: {viewCount, likeCount}, ...}.
• Add error recovery hints in descriptions. E.g., for channels_getChannel: 'Returns error 404 if the channel ID is invalid. Use search_list to find a channel by name, then extract the channelId.'
• Clarify tool distinctions in descriptions. For channels_list vs channels_getChannel: 'channels_list discovers multiple channels (discovery tool); channels_getChannel retrieves details for a single known channel (detail tool).' Similar guidance for list vs get variants.
• Replace open-ended 'part' parameters with enum constraints listing valid property names (e.g., part enum: [snippet, statistics, contentDetails, status] for channels_list). Validate on the server and return clear errors if invalid parts are passed.
• Add pagination guidance: 'maxResults: 1-50 (default 20). Use with cursor or offset to iterate large result sets. Returns next_cursor in response when more results are available.'
• Implement per-tool error recovery. Return structured errors like {error: 'not_found', resource: 'channel', suggestion: 'Try channels_list or search_list to find the channel by name.'}.

Inferred effective spec: <=2025-11-25.

• Relies on Stateful initialize / Mcp-Session-Id (removed; protocol is stateless) - make each request self-contained