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

Annotations already declare readOnlyHint and openWorldHint, and the description adds substantial value beyond them: the credit cost model with a worked example, the ranking basis, and a caveat about how results must not be interpreted. This is exactly the kind of extra behavioral context that annotations cannot carry.

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?

Two sentences with no filler: the first defines the operation and its output, the second front-loads the scope limitation and then the cost. Every clause earns its place.

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 description compensates by describing the return content and its ordering, and it adds the cost and interpretive caveats an agent needs before invoking. Nothing material is missing for a read-only, 3-parameter comparison tool.

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 67%, with patterns, defaults, and the marketplace code list already documented in the schema. The description adds no parameter-level detail (e.g. ASIN format, marketplace codes, competitor cap) beyond what the schema provides, so the baseline of 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 precise verb+resource ('compare the TEXT of your Amazon listing with up to 5 competitors') and the exact output ('words/phrases that appear in their titles and bullets but not in yours, ranked by how many competitors use them'). It also explicitly distinguishes itself from search-ranking/search-volume tools, so an agent can separate it from siblings like amazon_search or amazon_listing_audit.

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 clear context for when this applies (listing-copy comparison, up to 5 competitors) and an explicit exclusion ('it is not search-ranking or search-volume data'), plus a cost rule (1 credit per listing compared). It does not name a specific sibling to use instead when the user actually wants ranking data, which keeps it short of a 5.

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