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

The annotations already declare readOnly, idempotent, non-destructive, and closed-world, so the safety profile is covered. The description still adds genuinely new context: the call is free, results are permission-scoped to the paying wallet, and the response includes a signature check plus settlement state. It stops short of describing edge behavior (e.g., what happens for an unknown or non-owned receipt_id), which keeps it off a 5.

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?

Roughly four short statements, all front-loaded with the verb and return contents before the disambiguation clauses. Nothing redundant; even the one-word "Free." carries a real selection signal.

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 an output schema present, the description does not need to enumerate return fields, and it still summarizes them. Annotations cover the safety profile, the schema covers parameter formats, and the description covers routing and the authorization constraint — nothing an agent needs to invoke it 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 description coverage is 100% and both parameters are documented there, including the emb_+24-hex format and the account-scoping note on agent_wallet. The description's "wallet must be the one that paid" largely restates the schema's own wording rather than adding new meaning, 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?

The description opens with a specific verb and resource ("Look up one of your own receipts by receipt_id") and enumerates what comes back: the stored signed receipt, its signature check, and settlement state. It also explicitly separates the tool from receipt_history and check_url_custom, so an agent can distinguish it from siblings without opening any 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?

Routing is explicit: "One receipt by id: this tool. Your whole history: receipt_history. A check on a URL: check_url_custom." Each alternative is named with the condition that selects it, and the "wallet must be the one that paid" line states a precondition for use.

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