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

The annotation readOnlyHint=true already covers the safety profile as a read operation. The description adds only the REST endpoint (GET) and does not disclose additional behavioral traits like error responses, pagination, or return format, providing no value beyond 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?

The description is two concise sentences, front-loading the purpose and immediately followed by the REST endpoint. There is no filler or redundant 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 simple get-by-id tool with a readOnlyHint annotation, the description is mostly complete. It lacks explicit mention of the return payload, but given the simplicity and the annotation, it is adequate for invocation.

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 has 100% coverage for the single 'id' parameter with a clear description ('The subscriber id.'), so the description's reference to 'by id' adds no new meaning beyond what the schema already provides.

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 'Get a single subscriber by id,' specifying both the verb (get) and resource (subscriber), and distinguishes it from sibling tools like gumroad_list_subscribers by emphasizing 'single' and 'by id.' The REST endpoint further reinforces the exact action.

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 purpose implies usage when a specific subscriber id is known, but there is no explicit guidance on when not to use this tool or mention of alternatives such as gumroad_list_subscribers for retrieving all subscribers. The context is clear but not elaborated.

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