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

Annotations already declare readOnlyHint and openWorldHint, so safety is covered. The description adds genuine behavioral context beyond that: the data is 'sourced from the same anonymous mobile backend Nike's own app uses' and the result spans 'every purchasable color variant (across width groupings).' This provenance and variant scope are not derivable from the annotations.

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?

Front-loaded with the core purpose ('Full Nike product-group detail...') before the detail of what is returned. Two sentences, mostly earning their place, though the 'same anonymous mobile backend Nike's own app uses' phrase leans slightly toward marketing framing rather than functional information.

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 single-parameter read tool with an output schema and safety annotations already covered, the description supplies ample context: data provenance, variant scope, and the origin of the required key. Nothing essential to correct invocation is missing, though it leaves the sibling boundary implicit.

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% and the single parameter is fully documented in the schema itself ('Product rollup key, from a search result's products[].group_key field'). The description largely restates this cross-reference, adding only the 'rollup key' framing, so baseline 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 resource and scope: 'Full Nike product-group detail for one product's rollup key,' enumerating that it returns shared product copy plus every purchasable color variant with pricing, sizes, and images. Clear about what it does, but it never explicitly distinguishes itself from the sibling nike_product or nike_product_availability, leaving the agent to infer the boundary.

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?

It implies the usage flow by stating 'group_key is the same value nike_search returns as a products[].group_key field,' which links the tool to the search step. However, there is no explicit when-to-use vs. when-not-to-use statement nor any mention of the alternative siblings (nike_product, nike_product_availability).

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