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

Annotations already declare readOnly, idempotent, non-destructive and open-world. The description adds value beyond them: free-tier designation, the 32-league coverage scope, and the 404 fallback behavior for unsupported sports. It does not describe pagination or response shape, but the added context is substantive.

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?

The paragraph is dense but front-loaded with the core purpose and its return fields before coverage and use cases. Every clause carries information (metrics, leagues, 404 fallback, example queries). It is slightly long but not padded.

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 compensates by enumerating the returned stats. It covers coverage scope and failure behavior for unsupported sports. What remains thin is nothing critical for a read-only stats endpoint, though it could clarify whether the league list is exhaustive.

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 schema already documents all four parameters, including the optional since/until dates, name substring search, and sport_key examples. The description only implies league keys through the league list and adds no syntax or semantic detail beyond the schema, so 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 verb and resource ('Card stats per referee') and enumerates the returned metrics (graded matches, yellow/red cards, cards per match, last match, next appointment). This clearly distinguishes it from the sibling 'propline_get_referee_matches', which covers matches rather than card statistics.

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 use cases ('which EPL referee gives the most cards', 'who is refereeing Arsenal next') and an explicit usage instruction ('check it before a cards prop'). It also states a when-not condition: other sports return 404 with available_sports. It does not explicitly route to the sibling 'propline_get_referee_matches', so a 4 rather than 5.

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