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

Annotations already declare readOnlyHint and openWorldHint, so the safety profile is covered. The description adds genuinely new behavior: the 20-item batch cap and the partial-failure semantics (unrecognized barcodes are omitted and surfaced in not_found rather than failing the whole call). It does not mention rate limits or auth, but the partial-failure disclosure is valuable context beyond structured fields.

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 core purpose, then the input format, then error behavior and downstream use. No filler; every sentence 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?

An output schema exists, so return values need not be re-explained. Combined with the batch cap, partial-failure behavior, and the explicit hand-off to chewy_product/chewy_products, the definition gives the agent everything needed to invoke it correctly.

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 100%, so the comma-separated GTIN/UPC format is already documented in the schema. The description largely restates that format plus an example, adding little beyond what the schema provides, so the baseline of 3 is appropriate.

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 ('Resolves'), resource ('GTIN/UPC barcodes to their Chewy part numbers'), and scope ('batch of up to 20... in one call'). An agent can distinguish it from the downstream chewy_product/chewy_products it feeds, which are fetch tools rather than barcode resolvers.

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?

Explains the workflow context clearly: resolved part_numbers feed directly into chewy_product/chewy_products, so the agent knows this is a prerequisite step. It does not, however, explicitly contrast itself with name/category-based siblings like chewy_search or state when not to use it.

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