postSlackMessage

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

With no annotations provided, the description must carry the full transparency burden. It does disclose that the message is sent in the authenticated user's workspace, but it doesn't mention permissions, delivery guarantees, rate limits, or the irreversible nature of posting a message. The basic action is clear, but additional behavioral context is lacking.

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?

A single, front-loaded sentence that states the action, the target, and the scope. Every word earns its place; there is no padding or redundancy.

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?

For a tool with only two parameters and no output schema, the description sufficiently covers the core functionality. It names the action, the target (Slack channel), and the authentication scope. The parameter schema handles the rest, so no critical information is missing.

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 description doesn't need to compensate. The description adds only a slight nuance by saying 'text message' which maps to the message parameter, but it doesn't explain anything beyond what the schema already provides.

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 uses a specific verb ('sends') and resource ('text message to a specified Slack channel'), clearly distinguishing it from read-only Slack tools like listSlackChannels and from the sibling postTeamsMessage which targets Teams.

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 establishes clear usage context: use this whenever you need to post a text message to a Slack channel in the authenticated user's workspace. It does not explicitly mention alternatives or exclusions, but the sibling tools (e.g., postTeamsMessage) are implicitly excluded by naming Slack. No prerequisites or when-not scenarios are stated, so it doesn't reach a 5.

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