The Slack MCP server defines 5 tools with generally good naming conventions (verb_noun pattern: conversations_*, channels_list) and descriptions present for all tools. However, there are significant gaps in schema completeness, parameter descriptions, and output documentation. Tool descriptions are adequate but lack clarity on prerequisites, when to use each tool vs. alternatives, and actionable error guidance. Parameter schemas are mostly present but some lack proper type definitions and constraints. Output schemas are not documented. The server follows the chat-data-model reasonably well by accepting both IDs and names (e.g., '#general' or 'Cxxxxxxxxxx'), but lacks composition guidance and pagination detail in responses.

• Document output schemas for all 5 tools. For example, conversations_history should document: {messages: [{ts: string, user: string, text: string, thread_ts?: string}], next_cursor?: string}. This enables LLMs to extract chaining IDs and plan follow-up calls.
• Convert prose enum constraints to formal JSON Schema enums. channels_list should declare: 'channel_types': {type: 'string', enum: ['mpim', 'im', 'public_channel', 'private_channel']}. conversations_add_message should declare: 'content_type': {type: 'string', enum: ['text/markdown', 'text/plain']}.
• Standardize the 'limit' parameter type across all tools. Choose either: (a) accept both '1d' strings and numeric counts by documenting the grammar in the description and parsing server-side, OR (b) split into limit_messages (number) and limit_time (string like '1d'). Current mixed typing invites agent confusion.
• Add error recovery guidance to each tool description. Example for conversations_history: 'If the channel is not found, the response will indicate which channels exist. Use channels_list() first if unsure of the channel name. If you lack read permission, the response will indicate insufficient scope.'
• Expand channels_list description from 'Get list of channels' to ~100 characters: 'List all channels (public, private, direct messages) in the workspace. Call this first to discover channels before reading their history or posting messages. Results include channel ID, name, topic, and member count.'
• Document pagination structure in tool descriptions. Add to conversations_history, conversations_replies, conversations_search_messages: 'Results are paginated. If next_cursor is present in the response, pass it as the cursor parameter in a follow-up call to fetch the next batch. Do not set limit when using cursor.'

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

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