Harken is a well-structured audio transcription MCP server with three focused tools. Strengths: all tools have detailed descriptions (200+ chars each), complete JSON Schema input definitions with proper type constraints and regex patterns, explicit tool annotations (readOnlyHint, openWorldHint), and documented output schemas. The tool naming is clear and verb-based. Weaknesses: parameter descriptions are somewhat brief (not all include format/constraint details explicitly in the description text, despite being in the schema), and the tool set is narrowly domain-specific without broad composability patterns. All three tools are read-only operations with clear single responsibilities. Evidence: transcribe_file uses {type:string, description:'Absolute path...'} with schema visibility; transcribe_whatsapp_export includes regex pattern validation for date fields; output schemas for all tools are formally declared with detailed property descriptions.

• Restate parameter constraints explicitly in descriptions. Change 'Absolute path to the audio file' to 'Absolute path to the audio file (1 - 4096 chars, must exist on the filesystem)'.
• In transcribe_whatsapp_export schema, add a 'description' field to the messages[] items clarifying when 'text' is omitted: 'Each message object has date, time, sender. Transcribed messages include text, duration, language; failed or missing messages include error instead.'
• For transcribe_status, add a note in the parameter description: 'Accepts no parameters. Call to check whether the model file is cached and whether startup warm-up is complete.'
• Consider adding examples to the output schema descriptions to help LLMs understand the shape of responses (e.g., 'segments are in chronological order, non-overlapping').
• Document any rate limits, timeouts, or file size limits in tool descriptions. E.g., 'transcribe_file: supports audio files up to 4 GB; transcription may take several minutes depending on file length and CPU.'