Slack MCP Server

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations provided, the description carries the full burden of behavioral disclosure. It states the tool sends a message but does not mention any behavioral traits, such as permission requirements, rate limits, message formatting support (e.g., markdown), or error handling. This leaves critical operational details unspecified.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is a single, clear sentence that directly states the tool's function without unnecessary words. It is front-loaded and efficiently communicates the core purpose, making it highly concise and well-structured for quick understanding.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the complexity of a message-sending tool with no annotations and no output schema, the description is incomplete. It lacks details on behavioral aspects, error cases, return values, and differentiation from siblings, making it insufficient for an agent to fully understand how to use the tool effectively in context.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The input schema has 100% description coverage, fully documenting all three parameters (channel_id, text, thread_ts). The description adds no additional semantic context beyond what the schema provides, such as examples or constraints, so it meets the baseline for adequate but unenhanced parameter information.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the action ('send') and target ('a message to a Slack channel'), making the purpose immediately understandable. However, it does not differentiate this tool from its sibling 'slack_reply_to_thread', which also sends messages but in a specific context, leaving room for ambiguity in sibling selection.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description provides no guidance on when to use this tool versus alternatives like 'slack_reply_to_thread' for threaded replies or 'slack_upload_file' for file sharing. It lacks context about prerequisites, such as needing channel access or message formatting options, leaving the agent without usage direction.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.