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

Annotations already declare readOnly/openWorld/non-destructive, so the safety profile is covered; the description adds real context beyond that — a tennis-only scope restriction and an "Upstream cost: 1" budget signal that tells the agent this is a metered call. It does not discuss pagination or result limits, but with an output schema present that is a minor gap.

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-loads the capability, then uses labeled bullets for usage and exclusions — very scannable and mostly waste-free. Minor redundancy: "Optional surface/year filters" in the opening is repeated verbatim later as "Filters are surface (Hard/Clay/Grass/Carpet) and yearFrom/yearTo."

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?

For a 5-parameter read tool with an output schema and full annotation coverage, the description supplies what structured fields cannot: routing logic against three siblings, scope restriction, and cost. Only the tennis-only claim sits in mild tension with the game enum admitting lol/cs2/dota2/etc., but that reads as a server-side constraint rather than missing information.

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 game, playerId, surface, yearFrom and yearTo are already documented with examples and bounds. The description restates the surface values and year filters without adding syntax or edge-case meaning (e.g. how yearFrom/yearTo interact, or behavior when surface is omitted), so it sits at the baseline for a fully-described 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?

Opens with a specific verb+resource ("Tennis player career statistics") and enumerates exactly what aggregates come back: W/L totals, win percentage, titles, Grand Slam/Masters counts, plus per-surface and per-level breakdowns. An agent can distinguish this from player_profile and player_matches on the strength of the description alone.

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 example questions that select this tool, an explicit "Prefer over" clause naming two siblings with the reason each falls short (no breakdowns / no aggregates), and a "Do not use when" clause routing match logs and ranking-over-time to their own tools. When-to-use, when-not, and alternatives are all present.

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