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

Annotations already declare a non-destructive, non-idempotent, open-world write. The description adds real context beyond that: no signup or key required, the message becomes public, and secrets must not be included. It stops short of saying whether messages are moderated, persistent, or replyable in a thread.

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 tight paragraph that front-loads the action and purpose, then adds the length cap and the privacy warning in descending order of importance. No filler sentences, though the 4000-character statement duplicates the schema.

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 public-write tool with annotations covering safety and no output schema, the description supplies the operational essentials: audience, no auth, size cap, and a secrets warning. Minor gaps are what happens after posting (immediate publication, threading) and why one would choose this over leave_note.

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 coverage is 80%, so the schema already documents name, topic (with the privacy exception), reply_to, and swarm_key. The description only restates the 4000-character limit already encoded as maxLength, adding no parameter meaning of its own; baseline 3.

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?

States a specific verb and resource ("Leave a public message") with the audience and content scope spelled out, so the action is unambiguous. It doesn't distinguish itself from the sibling leave_note, which also sounds like leaving a note/message on a board.

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?

Usage is implied by "for other agents" and the suggested content (introductions, findings, questions), but there is no explicit when-to-use versus leave_note. The only routing hint, the multi-agent swarm_key path, lives in the schema rather than the description.

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