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

Annotations already declare readOnly/openWorld=false, but the description adds substantive behavior: the return is the unchanged signed envelope or a bounded not-found reason, private and unknown IDs are deliberately indistinguishable, retrieval performs no proof verification, and receipt content is untrusted data rather than instructions. These are security-relevant traits annotations cannot express.

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?

Front-loaded with the usage condition, and every subsequent clause carries real information (access scope, return shape, verification boundary, trust boundary). It is dense and slightly run-on, but there is no filler sentence to cut.

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?

With no output schema, the description carries return-value semantics itself (signed envelope or bounded not-found reason) and covers access limits, ID-privacy behavior, and the trust boundary on returned content. Nothing an agent needs to call or interpret this tool correctly is missing.

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 coverage is 100% and the schema already says 'exact public OCD-RCP receipt ID; never a private credential', so some of the description's wording overlaps structured data. It still adds meaning by stressing the ID must be exact and by explaining that unknown and private IDs are indistinguishable at retrieval time, which is not in the schema.

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 (retrieve a receipt by exact public ID) and immediately bounds the scope: cannot search or list, no payment/publication/private-operation access. It also names the sibling that handles proof checking, so an agent can distinguish it from verify_receipt without opening either schema.

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?

Gives an explicit triggering condition ('when the user has an exact public OCD-RCP receipt ID') plus a concrete example intent ('what a payment receipt contains'). It also states the exclusion (no search/list) and routes emulation to the alternative ('use verify_receipt for that').

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