Single tool server with generally adequate but not comprehensive definition quality. The tool `fetch_youtube_transcript` has a reasonable name following verb_noun convention, clear parameter descriptions with proper typing and enums, and an acceptable overall schema. However, the tool description is relatively generic and lacks specifics about output structure, error conditions, and practical guidance for LLM selection. The implementation shows input validation (checking format enum, type checking) but error messages are somewhat generic. Output schema is not explicitly documented, only the return type `str` is visible in the function signature. Parameter defaults are sensible (lang_code='en', format='json') and avoid destructive defaults. No pagination, batching, or advanced composition patterns are present, but the tool's domain (read-only transcript fetching) does not demand these. Schema quality is solid with proper enum constraint on format parameter, but lacks explicit output field documentation.

• Document the output schema explicitly. Clarify whether 'text' format returns plain text string vs. newline-separated items, and whether 'json' format returns a JSON string or an object. Add a structured example in a schema definition comment.
• Enhance the tool description to include: (1) What the output looks like (e.g., 'Returns a string containing the full transcript in your chosen format'), (2) When to use it ('Use to retrieve full video transcripts for summarization or analysis'), and (3) Common failure modes ('Transcripts may be unavailable if the video owner has disabled them').
• Improve error messages to guide recovery. Replace 'Transcripts are disabled for the video with ID...' with 'Transcripts are disabled for this video. The video owner may have disabled them. Check the YouTube settings or try a different video.'
• Consider adding a parameter to accept alternative language fallbacks (e.g., fallback_lang_code) if the primary language is unavailable, to reduce failures when requested language has no transcript.
• Document the acceptable language codes and provide guidance or a reference (e.g., 'Use ISO 639-1 codes like en, es, fr, de').