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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds essentially nothing behavioral beyond a field list that duplicates the output schema – no pagination, auth, error, or freshness context. With a simple read-only fetch this is tolerable but thin.

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?

A single front-loaded sentence listing the returned fields with no filler. It is efficient, though the field list is largely redundant with the output schema.

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?

Because an output schema exists, the description needn't explain return values, yet it spends its whole budget doing so while omitting the one thing the schema leaves undocumented: what the 'id' parameter should contain. Adequate but with a clear gap given it is the primary way to call this 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?

One required parameter with 0% schema description coverage, and the description never mentions it. An agent is left guessing whether 'id' is a numeric SKU, a slug, or a URL fragment, which is exactly the gap the description should fill when the schema is silent.

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 identifies a specific resource (a Costco product's detail) and enumerates the fields returned, so an agent can tell it apart from search-style siblings like costco_search. It never states the operation explicitly ('retrieve a product by id'), and it lists fields that overlap with siblings costco_product_availability and costco_product_reviews, so the boundary is slightly blurry.

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?

There is no guidance on when to use this tool versus costco_search, costco_product_availability, or costco_product_reviews, and no note that it requires a product id obtained elsewhere. Usage must be inferred entirely from the name and field list.

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