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

Goes well beyond the readOnly/openWorld annotations: discloses that the two halves are fetched in parallel and can fail independently, that 'limit' is enforced locally because the upstream completed route ignores ?limit=, and that the two halves overlap so the same matchId can appear twice. It also states parallel-safety and upstream cost (1 or 2 calls).

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 one-line summary followed by clearly labelled when-to-use / prefer-over / do-not-use sections and then behavioral notes. Dense but every clause carries operational information; slightly long, and the overlap warning could sit closer to the limit discussion.

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?

With an output schema present the description need not explain returns, yet it still documents scheduledCount/completedCount semantics and the duplicate-matchId hazard, plus failure independence and cost. Nothing needed to call it correctly is missing.

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, but the description adds real meaning: 'date' MUST be YYYY-MM-DD and defaults to today (UTC), 'limit' bounds EACH half while counts still report the full day, and 'include' selects the halves. The only gap is that the required 'game' parameter is never named — 'Tennis-only' implies the value but does not say it.

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+resource+scope: 'One day of tennis: the day's schedule and/or the matches completed that day, across ATP and WTA.' An agent can immediately distinguish this from upcoming_schedule, live_matches, and player_matches without opening any schema.

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?

Explicit 'When to use', 'Prefer over' naming call_api routes and the specific query-param reason (?date=), plus 'Do not use when' routing to live_matches and player_matches. Both the positive and negative conditions are enumerated.

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