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

Annotations already declare readOnlyHint and openWorldHint, so the description is not burdened with the safety profile. It nonetheless adds genuinely useful context the annotations do not: per-call cost ($0.002 USDC), the x402 payment rails (Base, Solana, Arc), and that failed calls are not charged — material for an agent's cost/retry decisions.

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?

Two sentences, front-loaded with what is returned and immediately followed by the scoping constraint and the billing terms. Dense and largely waste-free; the field enumeration is long but serves discoverability.

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?

A read-only, two-parameter fetch with an output schema, fully described schema params, and the one non-obvious operational fact (x402 pricing and non-billing on failure) disclosed. Nothing an agent needs in order 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 description coverage is 100%, with both `date` (YYYY-MM-DD, default yesterday UTC) and `tour` (enum-like values) documented in the schema itself, so the baseline is 3. The description only reinforces the date scoping ('one day', 'that day') and adds nothing about the tour variants.

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 names a specific source (TennisExplorer), a specific resource (ATP/WTA match results for one day) and enumerates the returned fields, so the purpose is unambiguous. It does not differentiate itself from adjacent siblings such as dev_flashscore, dev_sofascore_live or dev_wta_tennis_rankings, which keeps it at a 4 rather than a 5.

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?

Usage is implied by the 'one day' framing and the 'Only matches listed for that day' constraint, so an agent can infer it is a daily-results lookup rather than a rankings or live-score tool. However, no alternative is named and there is no explicit when-not guidance against the many other scoreboard/odds siblings.

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