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

The annotation (readOnlyHint: true) already communicates that this is a safe read operation. The description adds the optional email filter and the REST endpoint, but it does not disclose additional behavioral traits such as pagination, rate limits, or return format. This aligns with annotations and provides minimal extra context.

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 a single, concise sentence that front-loads the action and resource, and includes the REST endpoint for reference. There is no redundant or irrelevant text, making it highly efficient.

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 read-only list operation with only two well-documented parameters, the description is reasonably complete. It specifies the scope and optional filtering, though it does not mention the return structure or pagination, which would be useful but are not critical given the simplicity and read-only annotation.

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%, with both parameters already well-described. The description reinforces that email is an optional filter and product_id identifies the membership product, but it does not add new details beyond the schema. 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?

The description clearly states the action ('List') and the resource ('a membership/subscription product's subscribers') with an optional email filter. This distinguishes it from sibling tools like gumroad_get_subscriber (which retrieves a single subscriber) and other list tools by scoping to subscribers of a specific product.

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 implies usage (listing subscribers for a product, optionally filtering by email) but does not explicitly mention alternatives or when not to use it. No comparison with gumroad_get_subscriber or other list tools is provided, so the guidance is implied rather than explicit.

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