This server has TWO tools with acceptable naming (verb_noun pattern: list_channels, fetch_messages) and visible input schemas. Both tools have descriptions present. However, critical gaps emerge: (1) parameter descriptions are minimal and lack actionable constraints (e.g., 'ISO-8601 date string' without format spec or example); (2) NO output schema is documented anywhere, the LLM cannot know what fields to expect from list_channels or fetch_messages responses; (3) descriptions are brevity-focused but lack the 'WHEN to use' and 'WHAT to return' guidance that LLMs need for proper tool selection; (4) error handling is present in the CallToolRequestSchema handler but sanitized to a generic string ('Tool execution failed due to an internal error'), which provides NO recovery guidance to the LLM. The partial fetch_messages implementation shown (truncated mid-code) reveals internal data transformation (filtering bot messages, fetching user info, remapping Slack response fields) but this transformation logic is not declared as part of the tool contract, LLMs cannot plan for it. Per the rubric baseline (194 chars avg tool description, 72 chars avg param description), both tools fall short: list_channels description is 60 chars (acceptable low end); fetch_messages is 66 chars (acceptable low end); but parameters lack any description depth. Overall: definitions are PRESENT but INCOMPLETE. Serviceable for simple agents but insufficient for production autonomous reasoning.

• Add explicit output schema documentation to both tools. For list_channels: document that it returns {channels: [{id, name, is_private, topic, ...}], count}. For fetch_messages: document {messages: [{id, text, user_id, user_name, timestamp, date, thread_ts, reply_count, attachments, files}], total_count, oldest_timestamp, newest_timestamp}.
• Expand parameter descriptions with format specs and ranges. For since_date: 'ISO-8601 date string (YYYY-MM-DD or RFC3339). Messages are fetched back 7 days maximum. Example: 2024-01-15 or 2024-01-15T00:00:00Z.'
• Enhance tool descriptions to 150-250 chars, adding WHEN/WHY and return summary. E.g., list_channels: 'List all public channels in the Slack workspace. Call this first to discover available channels before fetching messages. Returns channel IDs, names, topics, and privacy settings.'
• Replace generic error message ('Tool execution failed due to an internal error') with actionable guidance mapped to specific failure modes. E.g., validation errors: 'Invalid conversation_id: must be a Slack channel ID (starts with C). Call list_channels() to see available IDs.' For rate limits: 'Rate limit reached. Retry in 30 seconds.' For missing channels: 'Channel not found. Available channels: #general, #engineering, #random.'
• Document bot message filtering explicitly in fetch_messages description: 'Fetches messages from a channel since a specific date. Returns only messages from human users; bot messages and automation events are excluded.'
• Add per-parameter validation rules. For conversation_id: add description 'Slack channel ID (e.g., C1234567890 or C1234567890ABCDEF12345678)' with pattern constraint in schema.

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

• Relies on Logging (deprecated) - log to stderr or use OpenTelemetry