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

The description goes well beyond the annotations by explaining that nothing posts, where the draft is saved, what older Slack installs show, and what the Send button does for channels where the bot is present. It also specifies the user's voice and formatting conventions, which is valuable behavioral context for a drafting tool.

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 front-loaded with the core action and non-posting behavior, followed by usage, fallback behavior, and style guidance. It is dense but mostly earns its length; the fallback UI explanation is useful but slightly niche.

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 drafting tool with no output schema, the description is complete: it covers what happens, where the draft goes, how to invoke it, when to re-invoke it, and how the text should be written. The schema fully covers parameters, so no important calling context 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 all five parameters are already documented in the schema. The description adds some destination clarity for to and channel_id, but does not explain team_id or thread_ts beyond what the schema provides, so the baseline of 3 is appropriate.

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 states a specific verb and resource: write/draft a Slack message for a person or channel. It also clearly separates this from sending by saying 'Nothing posts' and explaining that the result is saved as a draft in the user's own Slack.

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?

It gives clear triggering guidance: use whenever the user asks to write, draft, or prepare a Slack message, and call again with revised text for changes. The non-posting behavior implies this is not the send tool, but it does not explicitly name send_slack_message as the alternative when the user actually wants to send.

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