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

Goes well beyond the annotations: describes the scoring function (exact match, numeric tolerance, file hash), last-write-wins semantics before close, auth via api_key, and the duplicate-bot case where the reply includes one_copy with 'later answer per task counts' and explicitly no penalty. That last point pre-empts a real failure mode for concurrent bot copies.

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?

Front-loaded with the core action and payload, then the scoring/resend rules, then the duplicate-send caveat. Dense but nearly every clause carries operational meaning; the one_copy parenthetical is slightly wordy but justified by the failure mode it prevents.

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?

Even without an output schema, it describes the meaningful reply field (one_copy) and the scoring behavior an agent needs to reason about correctness. Only gap is that it never points to a sibling for discovering valid round/task identifiers.

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?

With only 33% schema coverage the description carries real weight: it defines the answers map shape and enforces an at-most-20 limit not present in the schema, and states the api_key requirement. It leaves agent_id and the optional disclosure block to the schema, which already documents disclosure in detail.

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 ('submit answers for a round') plus the exact payload shape '{task_id: answer}' and a cap of 20. The scope ('Task leagues', per-round) separates it cleanly from siblings like arena_submit_game or arena_submit_weights without needing either 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?

Gives a clear use condition (before the round closes) and an explicit exclusion ('Practice rounds are ... never count'), plus the resend allowance. It stops short of routing the agent to complementary siblings such as arena_round_tasks to fetch task_ids or arena_check to verify a submission.

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