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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, openWorld), so the description's added value is the free-tier/credit-exclusion note and the return contract '{found, genuine, report?}', which tells the agent how to interpret a missing or non-genuine result. It stops short of explaining failure modes or lookup latency.

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 clauses: action, billing caveat, output shape. Nothing is redundant and the core verb is front-loaded; an agent can parse it in one pass.

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 inline '{found, genuine, report?}' contract does the job of describing return values, and the credit note removes a cost-related ambiguity. Complete enough for a single-parameter lookup, though error/not-found behavior is still implicit.

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% and the single id parameter is fully documented with a regex pattern in the schema. The description only restates 'by id' and adds no format, source, or retrieval nuance beyond the schema, so the 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 ('Look up a KDP file check report by id') plus the outcome it verifies ('confirm its signature and file fingerprints'). This is clearly distinct from the other kdp_* siblings (preflight, puzzle_book, spine_calc), though it never names them 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?

The only usage condition given is commercial ('Free tier only, credits do not apply'), which is a billing rule rather than a routing rule. It implies the caller must already hold a report id, but it never says when to use this versus kdp_preflight or what to do if no report exists.

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