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

Annotations already declare read-only and non-destructive behavior, and the description adds meaningful details: parallel-safety, upstream cost formula, name resolution via player search, cell orientation as W-L from the row player's perspective, and '-' on the diagonal. No contradictions 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-structured into purpose, usage, exclusions, and behavior sections with no filler. Every sentence carries routing, semantics, or cost information, and the most important scope constraint appears early.

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 2-parameter tool with an output schema, this is complete: it covers player limits, input forms, cell semantics, routing to alternatives, and upstream cost. Return-value details are covered by the output schema, so the description does not need to repeat them.

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 value by explicitly restricting the tool to tennis despite the multi-game enum and by clarifying that names resolve via player search. The only wrinkle is the schema's game enum/examples implying other games, but the explicit 'Tennis-only' statement compensates.

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?

The description opens with a specific object: a multi-player tennis head-to-head grid showing each pair's series record. It names the adjacent sibling head_to_head and positions itself as the matrix form for N-player fields, so an agent can immediately distinguish it.

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?

It explicitly states when to use the tool (draw/field analysis, group-stage/semifinal comparisons), what to prefer it over (N head_to_head calls or raw call_api), and when not to use it (two-player deep-dive → head_to_head, stat leaders → leaderboard_*, rankings → standings). This is complete routing guidance.

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