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

Annotations already declare readOnly, idempotent, non-destructive, closed-world behavior, so the safety profile is covered. The description adds one genuinely behavioral fact — the Premier League default when neither team nor league is supplied. The international-break fallback lives in the schema, not the description, so added value is modest.

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 the purpose, then usage examples, then the default. Zero filler; each sentence carries information an agent needs.

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, low-complexity list tool with full schema coverage, the description covers purpose, usage, and defaults adequately. It does not describe the returned fixture shape (the 'say line' and us_eastern fields are only hinted at inside the country parameter), which matters slightly since there is no 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?

Schema description coverage is 100%, so every parameter (days, team, league, country) is already documented with bounds, defaults, and fallbacks. The description only implies that team/league are optional via the default sentence and adds no format or syntax detail beyond the schema. Baseline 3 applies.

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 resource and scope ('upcoming fixtures for a club or a league'), which cleanly separates it from siblings like get_results and get_table. The example queries reinforce the intent, though it never explicitly names which sibling to use instead.

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 when-to-use triggers ('who do Liverpool play next?', 'what's on in La Liga this weekend?') and states the no-argument default (Premier League). No explicit when-not or rival-tool routing is given, but the context is clear.

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