Slack MCP Server

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

With no annotations provided, the description carries full burden for behavioral disclosure. It mentions the action ('Reply') and a parameter effect ('broadcast'), but doesn't disclose important behavioral traits like required permissions, rate limits, error conditions, or what happens when replying to archived threads. The description provides basic operational context but misses critical behavioral details.

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 efficiently structured with a clear purpose statement followed by well-organized parameter explanations and return value indication. Every sentence serves a purpose with zero wasted words, and information is appropriately front-loaded.

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 tool's moderate complexity (4 parameters, mutation operation) with no annotations but an output schema, the description provides good coverage. It explains all parameters thoroughly and indicates the return format. However, for a mutation tool with no annotations, it should ideally include more behavioral context about permissions and error handling.

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?

With 0% schema description coverage, the description fully compensates by explaining all 4 parameters with clear semantics: channel_id identifies the channel, thread_ts identifies the parent message, text is the reply content with format information, and broadcast controls visibility. The description adds significant value beyond the bare schema.

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 specific action ('Reply to a message thread in Slack') with the resource identified ('message thread'). It distinguishes itself from siblings like 'post_message' (general posting) and 'send_dm' (direct messages) by focusing specifically on threaded replies.

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 implies usage context (replying to threads in Slack) but doesn't explicitly state when to use this versus alternatives like 'post_message' for non-threaded messages or 'send_dm' for direct messages. No guidance is provided about prerequisites or when not to use this tool.

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