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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), so the description adds real value beyond them: the 5-credit cost and the specific tie-break rule that 'making the cut beats missing it'. Return shape is disclosed too. Not fully exhaustive on pagination/limits, hence 4.

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?

One front-loaded sentence that opens with the use case and packs the key facts (contents, filter, cost) with no filler. The enumeration of return contents is slightly redundant given an output schema exists, keeping it from a 5.

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 detail return values, and it still conveys cost, scoping, and comparison semantics. Sufficient for an agent to call correctly; only minor gaps around how player IDs are resolved across leagues.

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 the schema already documents player_a, player_b, league, and season. The description only restates season filtering and adds no format, ID-source, or defaulting guidance beyond what the schema says. Baseline 3 is appropriate.

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 ('compare two players') and enumerates exactly what the comparison contains: shared tournaments, finishes, head-to-head winner logic, round-by-round strokes, and a summary. This inherently separates it from single-player siblings like get_player_results or get_player_stats, though no sibling is named explicitly.

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?

'Use to compare two players' gives clear context, and 'Filter by season' plus 'Costs 5 credits' tell the agent how to scope and budget the call. No explicit when-not or named alternative (e.g., use get_player_results for a single player) is given, 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.