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

Annotations already declare readOnlyHint=true, openWorldHint=false and destructiveHint=false, so safety is covered. The description adds genuinely non-obvious behavior: the returned payload includes both formula components, a league page URL, and a European rank that is absent for non-European leagues. It stops short of describing error behavior for an invalid slug.

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?

Content is front-loaded with the core purpose before the formula, and every clause carries information. The single dense sentence packing formula, defaults, bounds, and rank rules is heavy to parse, but little is wasted.

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 no output schema, the description takes on the burden of explaining return values and does so: components, rating points, page URL, and rank presence. It is nearly complete for a 2-parameter read tool, with only failure modes and parameter-interaction precedence left unstated.

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 0%, so the description must carry the load, and it largely does: `league` is identified as a slug obtained from resolve (explaining the regex), and `n` is described as the count of top European leagues with a default of 10 and range 1–20. The implied either/or relationship between the two parameters is conveyed but not stated explicitly.

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+resource ('Returns the 442 League Index') and spells out the exact composite formula, so an agent knows precisely what value comes back. It does not differentiate itself from the similarly-named sibling league_strength or rankings, which leaves ambiguity about which metric to prefer.

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 only implied: the parenthetical '(its slug from resolve)' signals that resolve must be called first to get a slug, and the default/bounds for `n` are stated. There is no explicit statement of when to use this versus league_strength or rankings, and no guidance on what happens if both `league` and `n` are supplied.

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