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

There are no annotations, so the description carries the burden of behavioral disclosure. It adds useful context that the operation is free and that the receipt id originates from every paid call, and 'look up' implies a read-only operation. However, it does not describe behavior for invalid or missing ids, nor does it explain the format or usage of the verification key.

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 'Free' signal and immediately states the operation, target resource, and return value. There is no wasted wording.

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 one-parameter lookup tool with no output schema, the description names both the input (receipt id) and the expected return elements (receipt and verification key). It is slightly incomplete about error handling or how the verification key should be used, but enough for an agent to invoke it 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?

The schema only defines 'id' as a UUID with a pattern, and schema description coverage is 0%. The description compensates by explaining that this id is the delivery receipt id returned from paid calls and that the tool returns the verification key alongside it.

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 uses a specific verb ('Look up') and a clear resource ('signed delivery receipt') plus the associated 'verification key'. It also distinguishes itself from the sibling tools by describing a receipt-lookup workflow that is not covered by health, menu, same_stock, or the st0x_* family.

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 note that the id is 'returned with every paid call' gives the agent clear context for when to invoke receipt: after executing a paid call. It lacks explicit exclusion statements or named alternatives, so it falls just short of an explicit when-not/alternative distinction.

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