Server has 5 tools with complete input schemas and descriptions. Naming follows verb_noun pattern (feishu_create_document, feishu_write_document_content, etc.). Descriptions are present and moderately detailed (avg ~150 chars), explaining WHAT each tool does. However, critical gaps exist: (1) NO output schemas documented anywhere, LLMs cannot predict return structure; (2) feishu_call_api is dangerously generic with no constraints on path/method, inviting misuse; (3) parameter descriptions lack format constraints (e.g., document_id format, folder_token structure); (4) no error handling guidance, tools fail silently with API errors; (5) feishu_send_message lacks receive_id_type default behavior clarity. Tool composition is reasonable (separate create/write/read/send), but lack of output documentation and error recovery patterns prevents higher scores.

• Document output schemas for all tools. Example: feishu_create_document should return {document_id: string, document_url: string, folder_token: string}. This enables LLMs to chain calls and extract needed fields.
• Add format constraints to parameters. E.g., 'document_id: string (format: UUID or alphanumeric, 20-40 chars)' and 'folder_token: string (format: opaque token from feishu_create_document or list_folders)'. Include in parameter descriptions.
• Restrict feishu_call_api to read-only methods (GET) or require explicit confirmation for destructive operations (DELETE, PATCH, PUT). Add an enum constraint: method: [GET, POST] with a note that destructive operations require a separate confirm_api_call tool.
• Implement error handling with recovery guidance. Catch API errors and return structured responses like {success: false, error_code: 4001, error_message: '...', recovery_hint: 'Check that document_id is valid. Call feishu_get_document to verify.'}.
• Expand feishu_get_document description to ~100 chars: 'Retrieve the full text content of a Feishu document. Returns plain text with line breaks preserved. Use this to read document state before writing or to verify content was saved.'