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

Annotations already declare readOnlyHint and openWorldHint, and the description adds substantive context beyond them: the API needs no key yet costs $0.002 USDC per successful call via x402 (Base, Solana or Arc), and failed calls are not charged. That billing/auth detail is exactly the kind of behavior an agent must know before invoking. It stops short of describing pagination or response behavior, but an output schema exists.

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?

It is front-loaded with the data payload, then the default-date behavior, the men's-only scope, and finally the pricing constraint — each sentence carries information. It is dense for three sentences but nothing is pure filler; the parenthetical about a keyless public API could be trimmed as it is partly implied by the pricing note.

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 two-optional-parameter, read-only lookup with an output schema, the description covers the essentials an agent needs: dataset scope, date selection, and the paid-call model. The only remaining gaps (limit semantics, result ordering, pagination) are either handled by the schema or unnecessary given the output schema.

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?

With 100% schema coverage the baseline is 3, and the description earns above that by explaining what a dateId actually represents (a ranking date listed on FIFA's site) and confirming the default is the latest date at build time. The 'limit' parameter is left entirely to the schema, so it isn't a full 5.

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 verb and resource ('FIFA men's national team world ranking') and enumerates the returned fields (position, team, country code, points, previous rank), so an agent can tell it apart from the other ranking siblings (owgr golf, world rugby, Leiden, etc.) at a glance. 'Men's ranking only' further narrows the scope against a possible women's dataset.

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 gives concrete usage context: the default date is the latest listed on FIFA's site, and 'pass dateId to read another listed date' tells the agent exactly how to switch dates. It doesn't name a specific alternative tool for women's rankings or when NOT to call it, so it falls short of an explicit when/when-not/alternative rule.

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