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

The readOnlyHint annotation already indicates a safe read operation. The description adds the definition of custom fields and the REST endpoint, providing some additional context. However, it does not disclose any further behavioral traits such as pagination, error behavior, or response format, which is a minor gap given the lack of an output schema.

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?

The description is two sentences, front-loaded with the purpose and including a useful REST endpoint reference. Every word earns its place with no redundancy.

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 simple list operation with one parameter, a readOnlyHint annotation, and no output schema, the description covers the core essentials: what it does and the resource. It could explicitly mention that it returns a list, but 'List' strongly implies this. The lack of detail on response structure is acceptable given the simplicity.

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?

The schema already provides 100% coverage for the single parameter 'product_id' with the description 'The product id.' The tool description reinforces that this is the product whose custom fields are listed, but it does not add substantial meaning beyond the schema. The baseline for high schema coverage is 3.

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 clearly states the action (List), the resource (a product's custom fields), and provides context on what custom fields are (extra fields collected at checkout). It also includes the exact REST endpoint, which unambiguously identifies the operation and distinguishes it from sibling list tools for other resources.

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?

The description clearly implies the use case: retrieving custom fields for a specific product. It does not explicitly discuss alternatives or exclusions, but the resource specificity itself distinguishes it from other list tools. Given the straightforward nature of the operation, this is adequate.

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