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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so the safety profile is fully covered by structured data. The description adds only the max-25 cap, which the schema already states, and says nothing about ordering, tie-breaking, or what happens when minMatches filters out the caller. Adequate but thin beyond annotations.

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?

The core is two compact clauses and is reasonably front-loaded, but the leading 'stats_leaderboard.' merely restates the tool name and the trailing 'Example: stats_leaderboard {}' conveys only that all parameters are optional. Roughly a third of the text is filler.

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 described, and the four optional parameters are fully documented in the schema. What remains is minor: sorting order and whether the leaderboard is bounded by season are unstated, but nothing prevents a correct call.

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%, so key, game, limit and minMatches are all documented in the schema, setting the baseline at 3. The description reinforces the 'overall vs per game' semantics of the game parameter and the 25 cap, but adds no new meaning for minMatches or key beyond the schema text.

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?

'Elo ranking overall or per game (max 25)' states the resource and the ranking metric concretely, and the description explicitly contrasts itself with arena_leaderboard and stats_bot, so an agent can distinguish it. The leading 'stats_leaderboard.' repeated name adds nothing, and the purpose is a noun phrase rather than a verb, keeping it short of a 5.

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?

'WHEN: Elo ranking overall or per game' plus explicit differentiators against arena_leaderboard (raw scores, today/all-time, game or tournament_id) and stats_bot (single card) give real selection guidance. It stops short of 5 because it never states a when-NOT condition or tie-breaker beyond the parenthetical descriptions.

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