This Slack MCP server has 8 well-named tools with complete input schemas and descriptions. However, there are significant gaps in parameter descriptions, output schema documentation, and error handling guidance. The naming convention is strong (all start with action verbs: slack_list, slack_post, slack_reply, slack_add, slack_get). Descriptions are present but terse (averaging ~60 chars), falling short of the 194-char baseline for production tools. Parameter descriptions are mostly present but lack detail on constraints, ranges, and expected formats. Output schemas are not documented, LLMs cannot reason about what fields to expect from tool responses. No error handling guidance or recovery paths are provided. The tool set is well-composed with clear single responsibilities, but lacks the detail needed for confident LLM invocation at scale.

• Document output schemas for all 8 tools. For each, specify: response type (object/array), field names, field types, which fields enable chaining (e.g., 'message_ts' from slack_post_message feeds to slack_reply_to_thread). Use a formal output schema comment above each tool implementation or in a separate schema file.
• Expand tool descriptions to 100-200 chars. Include WHAT the tool does, WHEN to use it vs similar tools, and key assumptions. E.g., 'List public channels in the workspace with pagination. Archived channels are excluded. Call this first to discover available channels before posting. Supports cursors for large workspaces.'
• Add min/max constraints to numeric parameters in JSON Schema. For 'limit' params: add 'minimum': 1, 'maximum': 200 to inputSchema. This is machine-parseable and prevents absurd values.
• For 'reaction' parameter in slack_add_reaction, provide examples of valid emoji names or link to Slack emoji documentation. Better: if the set of valid reactions is bounded, replace free-form string with an enum in the schema.
• For 'thread_ts' parameters, replace terse description with: 'The message timestamp in Slack format (YYYYMMDD.XXXXXX or Unix timestamp with 6 decimal places). If unsure, retrieve via slack_get_channel_history first.'
• Add error recovery guidance to WRITE tools. E.g., slack_post_message: 'If channel_id is invalid, call slack_list_channels to find the correct channel ID. If you lack permissions, the Slack workspace may have channel restrictions.'
• Implement optional confirmation mode for slack_post_message and slack_reply_to_thread. Add a dry_run or confirm_before_post parameter (default false). When true, return a preview of the message without posting, enabling agent verification.