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

Annotations already declare readOnlyHint and non-destructive behavior; the description adds valuable context: only players facing at least 50 break points qualify, season defaults to 2026, omitting tour yields the combined board, and it is parallel-safe with upstream cost 1. No contradiction with 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?

Well organized with labeled sections, front-loaded key result, and minimal fluff. Slight deduction because the 'When to use' bullet repeats the opening definition almost verbatim.

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 the description need not explain return shape. It covers selection criteria, defaults, filtering threshold, parallel-safety, and routing to alternatives. Nothing essential is missing for 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 coverage is 100%, so the baseline is 3. The description adds genuine parameter meaning by restricting usage to tennis despite the schema's broader game enum and clarifying that omitting tour produces the combined board. Limit and season are already well documented 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 exactly what the tool returns: share of break points saved per player, from real match-stats aggregates, ordered highest percentage first. This clearly distinguishes it from siblings like leaderboard_break_conversion and leaderboard_aces.

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?

Provides explicit 'When to use', 'Prefer over', and 'Do not use when' sections with concrete alternative tools (standings, rankings_movers, player_form, call_api). An agent can confidently select or reject this tool without opening sibling schemas.

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