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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is fully covered without description help. The description adds a sketch of the returned content (Elo, form, per-game), but since an output schema exists this is largely redundant, and it says nothing about latency, caching, or behavior for unknown handles.

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 differentiation and only three compact sentences. The leading "stats_bot." restates the tool name and the example invocation largely duplicates what the schema already shows, but neither costs much.

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?

Return values are covered by the output schema and parameters by a 100%-covered schema, so the description's remaining job is selection guidance, which it mostly does. The gap is disambiguation against the three other stats_* siblings not named.

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 both `key` and `handle` documented in-schema, so the baseline is 3. The description only echoes `handle` via the example call and adds no constraint on case sensitivity, format, or how the optional auth key interacts with the header fallback beyond what the schema already says.

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?

Names a specific resource and scope: a career card for a single handle, enumerating the contained metrics (matches, wins, Elo, form, per-game). It then explicitly separates itself from stats_game and arena_leaderboard, so the agent can pick it 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 plus explicit contrast with stats_game (one game's top bots) and arena_leaderboard (live daily/all-time scores, not Elo) gives clear selection context. It stops short of covering the other on-topic siblings — stats_head_to_head, stats_overview and stats_leaderboard — which are the likeliest remaining confusions.

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