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

Annotations already cover the safety profile (readOnlyHint, openWorldHint), and the description adds genuinely useful behavior: empty results are legal for a path with no competitions, and the returned id format is shown concretely (the 2026/27 Bundesliga example). It stops short of describing pagination or any rate/coverage caveats, which keeps it from a 5.

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?

Four tight sentences, front-loaded with what is returned, then the id's role, then the empty-result caveat, then the call ordering. Nothing is redundant with the title or repeated unnecessarily.

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 needn't explain return values, and it instead supplies the two things structured fields can't: where the required ids come from and what to do with the resulting competition id. Nothing needed to call this 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 meaning the schema does not: it frames federation, season, competition type, team type, league and area as components of a single selector path (conjunctive lookup) rather than independent filters. The example id illustrates the output key shape but not individual parameter values beyond what the schema documents.

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 ('Returns the competitions (Staffeln)') plus the exact lookup key combination, and explicitly separates itself from the sibling options endpoint and the downstream matchday/table/top-scorer endpoints. An agent knows precisely what this tool produces without opening the 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?

Gives an explicit prerequisite chain ('Use fussballde_competition_options to find the team type, league and area ids this tool needs') and names the follow-up tools to call with a returned competition id. It also pre-empts a likely misuse by declaring that an empty list is a valid result rather than an error.

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