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

Discloses non-obvious behavior well beyond the readOnly/idempotent annotations: it names no winner, no margin, no recommendation, each side carries its source rank, and out-of-panel measures (e.g. yards per attempt) are refused with nearest panel metrics. That refusal/error contract and the deliberate absence of a verdict are exactly what an agent needs before calling.

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?

Front-loaded with the core comparison behavior and packed with signal in three dense sentences. The em-dash clauses in the first sentence and the un-backticked `all:true` slightly reduce scannability, but there is little waste.

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?

No output schema and no parameter descriptions exist, so the description carries the burden, and it covers default behavior, metric input format, and refusal handling thoroughly. The gaps are the undocumented `season` parameter and the assumed semantics of `a`/`b`, which keep it from being fully complete.

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?

With 0% schema description coverage, the description must compensate. It explains `metrics` well (verified keys like "qb_anya.any_a" or plain-English names, max context) and `all` by implication, but never mentions `season` (2016–2026 constraint) and only implies `a`, `b`, and `entity_kind` via "two players or two teams." Partial compensation, so a 3.

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 (compare) and resource (two players or two teams), plus the exact scope of the comparison (position-relevant metrics by default). An agent can immediately distinguish it from get_entity_metrics or query_stat_leaders, which fetch rather than compare side by side.

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?

The description spells out the three operating modes and the condition that selects each — default, when `metrics` is set, and with `all:true` — which is clear usage context. It stops short of naming when to prefer this over siblings like get_entity_metrics, so no explicit alternative routing.

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