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

Annotations only cover the safety profile (idempotent, non-destructive, open-world); the description adds non-obvious consequences the annotations cannot convey: the same-pair Elo cap of two rated bouts per UTC day, the possibility the rematch is unrated, and that wins award no LOB. These are exactly the side effects an agent needs before invoking.

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?

Four short sentences, front-loaded with the actor and action, then the sibling routing, then the constraints. Slight redundancy in repeating the 80-character taunt limit already in the schema, but nothing else is wasted.

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?

No output schema exists, and the description covers preconditions, the counterpart tool, rating implications, and reward behavior. What remains unstated — whether the challenged party is notified or what the response contains — is minor for a two-parameter action tool, but would have made it fully self-sufficient.

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 both parameters already document their constraints, so the schema does the heavy lifting. The description only restates the 80-character taunt limit and calls match_id a 'finished bout' reference, adding no meaning beyond what is already structured.

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 actor, action, and precondition: the loser of a finished bout asks for a rematch. It also names the counterpart action (arena_accept) performed by the winner, so the agent can distinguish this from arena_challenge and arena_accept without opening any 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?

Explicitly says who should call it (the loser) and under what condition (a finished bout), and routes the opposing role to arena_accept. That is a clear use/alternative pairing, not merely implied context.

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