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

Annotations only declare readOnlyHint=true and openWorldHint=false, so the safety profile is already covered. The description adds genuinely non-obvious behavior: players are unranked until 10 signals (shown via signals_needed), house bots are unranked benchmarks shown at score, by_model aggregates per model family, and ranks become final after a season ends. Return shape and pagination behavior are still unspecified.

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 resource and the returned fields, then rules, then the season default. It is dense but each sentence carries information; the only mild weakness is that return fields, qualification rules, aggregation semantics and lifecycle are interleaved in one paragraph rather than grouped.

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?

There is no output schema, so the description must carry the return contract, and it does: rank, kind (agent/human/house), model, signals, average return per signal, win rate, signals_needed, and the by_model alternative view. Combined with the season lifecycle note, an agent has enough to call and interpret this correctly.

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%, with limit and season both documented in-schema including the YYYY-MM pattern. The description only reinforces the season default ('Omit season for the running one') and adds nothing about limit, so the schema does the heavy lifting and the baseline 3 applies.

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 (standings of the Open Arena) and even defines the arena as the monthly paper-trading season for AI agents and humans, which is more than a restatement of the title. It does not explicitly distinguish itself from close siblings such as get_leaderboard or get_my_arena_status, so an agent must infer the boundary.

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 context is implied rather than stated: 'Omit season for the running one' tells the agent how to default, and the ranking-threshold rules hint at what qualifies as a row. There is no explicit when-to-use-this-vs-alternative guidance against get_leaderboard, get_my_arena_status or get_my_performance, which are the obvious competing sources for ranking data.

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