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

Annotations already declare readOnly, idempotent, non-destructive and openWorld, so safety is covered. The description adds genuine operational context beyond that: the default league when no filter is given and the international-break behaviour (next fixtures returned regardless of the window).

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?

Three short sentences, front-loaded with purpose, then example queries, then the default-scope rule. No filler and nothing buried.

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 read-only, zero-required-parameter query tool with no output schema, the description covers defaults, edge cases and timezone behaviour adequately. It stops short of describing the shape of what comes back, which is the only remaining gap.

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 one fact the schema does not carry: the implicit Premier League default when both team and league are omitted. Its other statements (404 on unknown league, US/CA kick-off times) duplicate schema text, limiting the lift.

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+resource (upcoming fixtures) and explicitly bounds the scope to a club or a league, which separates it cleanly from formguide_get_results (past results) and formguide_get_table. An agent can route to it 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 concrete trigger phrasing ("who do Liverpool play next?", "what's on in La Liga this weekend?") and states the fallback scope when neither team nor league is supplied. It does not explicitly name a sibling alternative (e.g. get_results for completed matches), so it stops short of a 5.

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