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

Annotations cover the safety profile (readOnly, openWorld, non-destructive), and the description adds real behavioral context beyond them: sections relations/media/buybox are slower, missing marketplace yields no data and a 'MARKETPLACE NEEDED' answer, results are in local currency, and there is a mandatory account-notice output contract. It does not describe return shape or pagination, but the latency and failure-mode disclosures are 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?

Front-loaded with the differentiator against analyze_product, then usage, then marketplace handling, then output contract — a sensible ordering. It is long and repeats the marketplace rule already present in the schema descriptions, plus a lengthy verbatim-quoting instruction, which costs some tightness.

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?

For a read-only fetch tool with no output schema, the description covers scope, defaults, optional-section cost, prerequisite failure mode, currency semantics, and the account-notice output contract. An agent has everything needed to call it correctly and compose a reply.

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; the description still adds value by specifying the omit-sections default ('catalog + identifiers') and by reinforcing that marketplace must be user-supplied rather than assumed. The section meanings are largely duplicated from the schema, keeping it below 5.

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+resource (fetch extra catalog facts for one Amazon ASIN) and explicitly delimits scope against amzscout_analyze_product: what this tool adds and what it deliberately excludes ('No sales, price or review numbers'). The enumerated field list and the sections taxonomy make the purpose unmistakable relative to siblings.

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 an explicit when-to-call rule ('together with amzscout_analyze_product whenever the user asks about one specific product'), an explicit default ('call WITHOUT sections'), and per-section conditions for the optional sections. It also handles the marketplace prerequisite with a concrete ask-once-and-reuse policy and states the failure mode when omitted.

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