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

The readOnlyHint annotation already establishes this is a non-mutating read, so the description carries a lighter burden. It adds the REST endpoint mapping (GET /v2/sales/{id}), which is mildly useful for tracing, but says nothing about error behavior (e.g., unknown id) or auth requirements.

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?

Two short, front-loaded sentences with no filler; the purpose comes first and the endpoint mapping second. Every clause carries 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-resource getter with one fully documented parameter, a readOnly annotation, and no output schema, the definition covers what an agent needs to invoke it. Only the absence of any error/auth note keeps it from being fully complete.

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% and the single 'id' parameter is documented in the schema itself. The description's 'by id' merely restates the schema, adding no format or sourcing detail beyond it, so the baseline 3 applies.

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 and resource ('Get a single sale by id') and the 'single' qualifier implicitly distinguishes it from gumroad_list_sales. It stops short of explicitly naming the list tool as the alternative, so it is clear but not fully differentiated.

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?

Usage is only implied by the name and the 'single sale' phrasing; there is no explicit when-to-use or when-not-to-use statement, nor any mention of prerequisites such as owning the sale or required auth scope. An agent can infer the getter role from the sibling list_sales, but nothing is spelled out.

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