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 but offers minimal behavioral disclosure. It states this is an update operation (implying mutation) and mentions a success dictionary return, but doesn't cover critical aspects like authentication requirements, rate limits, edit time windows, permission constraints, or what happens to attachments/threads. For a mutation tool with zero annotation coverage, this leaves significant gaps.

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 appropriately sized and well-structured with clear sections (purpose, args, returns). Every sentence earns its place by providing essential information. The front-loaded purpose statement is followed by organized parameter explanations. Minor improvement could be merging the purpose and returns into a more cohesive flow.

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 a mutation tool with 3 parameters, 0% schema coverage, no annotations, but with an output schema (implied by 'Returns' statement), the description is moderately complete. It covers parameters well and mentions return format, but lacks behavioral context about permissions, constraints, and error conditions. The output schema existence reduces but doesn't eliminate the need for more operational 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?

Schema description coverage is 0%, so the description must compensate - which it does effectively by explaining all three parameters. It clarifies that 'channel_id' identifies the containing channel with an example format, 'timestamp' identifies the specific message, and 'text' is the new content. This adds meaningful context beyond the bare schema, though it doesn't specify timestamp format or text length limits.

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 ('Update') and resource ('an existing message'), making the purpose immediately understandable. It distinguishes from siblings like 'delete_message' and 'post_message' by focusing on modification rather than creation or removal. However, it doesn't explicitly differentiate from 'reply_to_thread' which might also update conversations.

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?

No guidance is provided on when to use this tool versus alternatives. The description doesn't mention prerequisites (e.g., needing edit permissions), constraints (e.g., time limits for editing), or when to choose 'update_message' over 'delete_message + post_message' or other sibling tools. Usage context is implied but not stated.

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