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

Beyond the read-only/idempotent annotations, it discloses that a signed-in member is required and that a key without a member returns the error member_required — exactly the kind of precondition an agent needs. It also states the fallback behavior (group filled from the member's team when filters are omitted), though it says nothing about result shape beyond 'top N' or pagination.

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, then usage triggers, then cohort definition, then auth. Four sentences with almost no waste; only the error-code sentence is arguably a footer rather than part of the narrative flow.

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?

Covers purpose, trigger phrases, cohort construction, defaults, and the auth failure mode for a 7-parameter tool with no output schema. The remaining gap is what the response actually contains (ranking entry, percentile, top-player list) — worth a line given no output schema exists.

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 already 100%, so baseline is 3; the description earns above that by explaining the joint semantics of ageBand/division/level — omitting them all silently defaults the cohort to the member's own team. That defaulting rule is the key behavioral nuance and is not in 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 verb and resource: it ranks a cohort by Desk level and returns the member's place within it. The scope is crisp enough to separate it from query_league_standings (team standings) and query_player_rating (single rating), though no sibling is named explicitly.

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 concrete user-phrasings that should trigger the tool ('where do I stand', 'how do I compare to the top players', percentile, top players in an age group) plus how to define the cohort. It never names an alternative tool or an explicit when-not-to-use condition, so there is no exclusion guidance.

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