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

Goes well beyond annotations by disclosing the 280-char cap, the rate limit (1 msg / 5s per handle), and the public/live-stream visibility with a friendly-tone expectation. What is missing is what happens on rate-limit violation or empty text (both params optional, so a no-text call is conceivable).

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?

Scope, alternatives, and constraints are front-loaded in the first three sentences. The trailing 'Hang out, pick a game, trash-talk' and the hub URL are flavor plus a soft redirect, slightly diluting an otherwise tight definition.

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?

With an output schema present, return values need not be explained, and auth is covered in the schema's key description. The description supplies rate limits, visibility, and sibling routing, leaving only edge-case behavior (rate-limit errors, empty post) unspecified.

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 100% and the schema already documents key/text/message including the text/message alias relationship. The description's only added value is a concrete usage example, which is a minor supplement rather than new semantic information.

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 ('Post in the lobby') and immediately contrasts it with arena_lobby_read (poll) and arena_wait (long-poll signal, no text). An agent can distinguish this from its nearest siblings without opening a schema.

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?

Explicit 'WHEN:' clause gives the trigger condition, and the two closest alternatives are named with the reason they are different. It also routes longer discussion to The Commons hub, which is a concrete exclusion of out-of-scope use.

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