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

Annotations already declare readOnly=true, non-destructive, open-world. The description adds useful context beyond them: results are 'current' only, no historical pricing, and a separate REST resource exists for offers/bestsellers. It stops short of mentioning rate limits, auth, or result freshness windows.

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, front-loaded sentences with no padding. The final sentence ('use REST amazon with resource') is slightly cryptic and relies on outside knowledge of a REST surface an agent may not have a tool for.

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 4-parameter read-only lookup with full schema coverage and no output schema, the description covers purpose, input constraint, and alternatives. Only minor gaps remain: no note on what a result object roughly contains or how asin vs query results differ in shape.

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 adds a constraint the schema does not formalize: 'Required: asin or query,' plus the implicit exactly-one relationship that is only partially hinted at by the query description. It does not add anything about results or marketplace beyond the schema.

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 ('Return current Amazon products by ASIN or keyword') and immediately names the sibling it is not (google_shopping_prices). An agent can distinguish it from search_walmart, search_ebay, and google_shopping_prices without opening any schema.

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?

Explicitly gives when-to-use ('Amazon lookups'), when-not ('not price history or other merchants'), and two named alternatives (google_shopping_prices, REST amazon for offers/bestsellers). Routing is unambiguous.

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