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

Annotations already declare readOnly/idempotent/closed-world, so the description correctly spends its words elsewhere: it discloses the credit cost ('Costs 1 credit') and the default-season behavior, both of which the annotations do not convey.

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?

Purpose and the sibling relationship are front-loaded in the first sentence, and the long league list is dense but each item disambiguates a slug. The enumeration is bulky, but little of it is filler.

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?

Output schema exists so return values need no explanation, and the description covers the two decision points (league, season default) plus cost. Only the 'soccer' vs 'Premier League' default naming is left slightly ambiguous.

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, and the description earns above that by mapping human-readable league names to enum slugs ('La Liga' -> laliga, 'Brazil's Serie A' -> brazil), which helps an agent pick the right enum value. Minor gap: it does not mention the 'soccer' enum value and instead calls the default 'the Premier League', slighting diverging from the schema's stated default.

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 and resource ('find club ids and abbreviations for a season') and explicitly positions itself relative to all siblings ('Every other tool takes a club as an id, abbreviation or name'), so an agent knows exactly what it retrieves and why.

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?

Gives clear usage context: call this to obtain club identifiers before invoking any other tool, and pass 'league' to scope it. It lacks an explicit 'don't use this for X' exclusion, but the prerequisite role is unambiguous.

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