Slack MCP Server

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

No annotations are provided, so the description carries the full burden of behavioral disclosure. It states what the tool does ('Get replies') but lacks critical details: it doesn't specify if this is a read-only operation, mention rate limits, describe pagination behavior (beyond the cursor parameter in the schema), or explain the return format. For a tool with no annotation coverage, this leaves significant gaps in understanding its behavior.

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 extremely concise—a single sentence with no wasted words. It's front-loaded with the core purpose, making it easy to scan and understand quickly. Every word earns its place, adhering to best practices for brevity in tool descriptions.

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 (a read operation with 4 parameters, 2 required), lack of annotations, and no output schema, the description is incomplete. It doesn't address behavioral aspects like safety, performance, or return values, leaving the agent with insufficient context to use the tool effectively beyond basic parameter input. More detail is needed to compensate for the missing structured data.

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?

Schema description coverage is 100%, so the schema fully documents all parameters (channel_id, thread_ts, limit, cursor). The description adds no additional meaning beyond what's in the schema—it doesn't clarify parameter relationships, provide examples, or explain semantics like how 'thread_ts' identifies the parent message. With high schema coverage, the baseline score of 3 is appropriate as the description doesn't compensate but also doesn't detract.

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 verb ('Get') and resource ('replies in a message thread'), making the purpose immediately understandable. However, it doesn't explicitly differentiate from sibling tools like 'slack_get_messages' or 'slack_search_messages', which might also retrieve message-related data, leaving some ambiguity about when this specific tool is uniquely appropriate.

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. It doesn't mention prerequisites (e.g., needing a specific channel ID and thread timestamp), exclusions, or comparisons to siblings like 'slack_get_messages' (which might handle non-threaded messages). Usage is implied but not explicitly defined.

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