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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so safety is covered; the description adds that this is a recorded-career snapshot rather than a live feed, which is meaningful behavioral context. It stops short of noting auth needs or that the 'top Elo' slice is bounded by the limit parameter, so it is not fully complete.

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?

Three short, front-loaded fragments that each carry information — purpose, selection rule, alternatives, and a call example. The only waste is the leading "stats_overview." restating the tool name that the agent already has.

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?

An output schema exists so return values need not be explained, both parameters are fully documented, and the description covers purpose and sibling disambiguation. Nothing an agent needs in order to call this correctly is missing.

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 (key, limit with default 5 / max 25) are documented in the schema, so the baseline is 3. The description's only added information is the `stats_overview {}` example implying a zero-argument call works; it adds no meaning about the limit or auth handling beyond the schema.

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 resource and scope: a high-level Arena career snapshot covering recorded matches and top Elo. It explicitly names and contrasts the two nearest siblings (stats_leaderboard for full Elo lists, arena_leaderboard for live daily scores), so the agent can separate it from them without opening 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?

The "WHEN:" clause gives a direct selection rule, and the following sentence supplies the exclusions plus the alternative to choose instead in each case. This is explicit when/when-not/alternatives routing, not implied guidance.

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