Slack MCP server has 12 tools with complete input schemas and descriptions, but quality is inconsistent. All tools have descriptions (10-100 chars, mostly adequate), and schemas include type definitions and required fields. However, descriptions lack LLM-optimized guidance on WHEN to use each tool vs. alternatives, and parameter descriptions are minimal (5-30 chars). No output schemas documented. Error handling is absent, no recovery guidance, no actionable error messages. Risk annotations (READ_ONLY, WRITE, DESTRUCTIVE) are present but not formalized as tool annotations in the schema. Naming is clear and verb-driven (list_, get_, create_, send_, etc.), but some tools conflate concerns (send_message accepts both text and blocks; update_message and delete_message are separate but could benefit from composition guidance). No pagination support visible for list_channels despite potentially large result sets.

• Document output schemas for all tools. E.g., list_channels should return [{channel_id, channel_name, is_private, topic, member_count, created_at}]. Include this in tool descriptions or a separate schema section.
• Expand parameter descriptions to 50-100 chars with format hints. E.g., 'Channel ID (format: C followed by 9+ alphanumeric chars, e.g., C1234567890) or channel name (e.g., #general).'
• Add error handling guidance to tool descriptions. E.g., 'Returns error if user is already in channel (retryable: no) or if channel is archived (retryable: no, suggest unarchive first).'
• Formalize tool annotations in schemas using readOnlyHint, destructiveHint, and idempotentHint fields to expose risk levels to LLMs.
• Clarify send_message parameter relationships: document that 'blocks' takes precedence over 'text' if both provided, or require exactly one.