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

With readOnlyHint/destructiveHint already covering safety, the description still adds genuinely non-obvious behavior: AMBIGUOUS_ENTITY is returned on multi-match name resolution, career stats are gated behind the Starter plan while profile/history still return on Free, and the headshot must be shown with its credit. Upstream cost 2–4 and parallel-safety further inform orchestration.

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 one-line summary followed by labeled sections (When to use, Prefer over, Parallel-safe, Example). Dense but every clause carries operational information an agent can act on; no filler or restatement of the schema.

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?

Covers the decision context (when/alternatives), failure mode (ambiguity), entitlement constraint (plan gating), and orchestration hints (parallel-safe, cost). An output schema exists, so return-shape detail is correctly omitted — nothing material is missing for correct invocation.

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 goes further by explaining that 'athlete' accepts either a slug or a name and that names are resolved through the league's search, and by tying includeStats to the Starter plan. That is real added meaning beyond the per-parameter schema text.

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?

Opens with a specific verb+resource+scope: a composite page combining profile, recent bouts, and career stats for RAF athletes / BKFC fighters. The league enum in the schema plus the 'composite' framing makes it immediately distinguishable from the granular siblings (combat_bout, combat_events, combat_h2h).

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?

Explicit 'When to use' with sample user phrasings, plus a named alternative: 'Prefer over: call_api profile + history + stats separately.' It also tells the agent when the tool is parallel-safe, which no sibling lists do.

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