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

Annotations already establish read-only, idempotent, non-destructive behavior. The description adds meaningful behavioral context beyond those annotations: the lookup is exact, the identifier is opaque, and enumeration is not supported, which shapes how an agent can expect the API to behave.

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 concise sentences deliver the action, the constraint, and the negative capability. No filler or redundant restatement of the tool name or schema is present.

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 point lookup with an output schema and read-only annotations, the description is fully sufficient. It communicates the necessary precondition, the absence of enumeration, and the lookup semantics; an agent has everything it needs to call the tool correctly.

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 0%, so the description carries the burden for parameter meaning. It effectively explains that receiptId must be the exact opaque identifier, adding semantic value beyond the schema's string pattern. Since there is only one parameter, this is sufficient.

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 states a clear action ('Retrieve one receipt') and a precise resource ('by its exact opaque identifier'), which fully defines the tool's purpose. It also explicitly clarifies that enumeration is not available, distinguishing this point-lookup tool from any imagined listing tool.

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 says exactly when to use the tool: when you already have the exact opaque identifier of a receipt. It also provides a clear exclusion, 'Receipt enumeration is not available,' telling agents not to attempt listing or discovery through this tool.

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