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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety and external-lookup profile is covered structurally. The description adds one genuinely useful non-obvious behavior: the returned URL omits ?tag= until real Associates IDs exist, which an agent would otherwise misread as a broken affiliate link. It says nothing about ambiguity handling, no-match results, or rate limits.

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 sentences, front-loaded with the capability, then the hard requirement, then the output quirk. No filler and no repetition of schema content beyond what is needed for context.

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 10 parameters, 20% schema coverage, no output schema, and only minimal annotations, the description carries substantial burden and does not meet it. Five parameters and the failure/no-match path are undocumented, which is a real risk given the tool's open-world lookup nature.

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 only 20%, with locale and marketplace described in the schema itself. The description names ASIN, URL, keywords, marketplace, and locale, but five parameters (stage, species, sizeBand, budgetBand, kitCategory) are never mentioned anywhere, so an agent has no way to know how they affect resolution or whether they are filters or fallbacks.

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?

The description names a specific verb (resolve) and enumerates the accepted input forms (ASIN, Amazon URL, keywords) plus the output (buyUrl / affiliateUrl) on a chosen marketplace. That is enough to separate it from siblings like search or add_item without opening the schema, though it never explicitly contrasts itself with search, which is the closest adjacent tool.

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?

'Requires marketplace + locale' states the prerequisite, and the input-mode list implies the valid call shapes. But there is no guidance on when to choose this over search (e.g. resolving an already-known ASIN vs. discovering products), nor any exclusion or fallback behavior when resolution fails.

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