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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so the safety profile is covered. The description adds real context beyond that: an mts_ key is required, provided via the X-API-Key header or the apiKey argument, with a free trial path and a paid plan with a 1,000-call allowance. It does not say what shape the receipt history takes, which keeps it below 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?

The tool's purpose is front-loaded in the first clause, and each following clause carries distinct operational information (auth, fallback, pricing). The pricing and quota sentence runs long and is the least essential part, but it is still actionable rather than filler.

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 read with three fully documented parameters and no output schema, the description covers the main caller-side unknowns: authentication, the keyless alternative, and quota/pricing limits. What is missing is a note on what the returned history contains or whether an unknown ref produces an error versus an empty result.

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 documents ref as an idempotency key, apiKey as the header alternative, and receiptId as an str_ id. The description only restates the apiKey requirement and does not clarify the either/or relationship between receiptId and ref beyond what the schema says, so 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: "Read a delivery receipt and its history." That cleanly separates it from the write siblings receipt_create and receipt_update, which act on the same resource. It does not explicitly name those siblings, so it falls short of a 5.

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 context is implied rather than stated: reading implies not creating or updating, and the auth requirement plus the routing to settle_trial_key for keyless callers is spelled out. There is no explicit statement of when to prefer this over receipt_update or how to choose between receiptId and ref, so the guidance is only implicit.

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