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

Annotations already declare readOnlyHint=true, so safety is covered. The description adds real behavioral detail beyond that: the missing_identifier error_code, that an example and next_action are returned, and that the underlying lookup is an anonymous public GET endpoint — useful auth and failure-mode context.

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?

Three short sentences, no repetition or filler, and the identity/identifier constraint is front-loaded ahead of the failure mode and endpoint detail.

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 should hint at what a successful status response contains (valid/expired/redeemed, balance, expiry). It only documents the error path, leaving the success payload shape undefined.

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 each parameter already documents the 'one of code, voucher_code, or voucher_id' rule, so the description's restatement adds little. The error-on-omission note is behavioral rather than parameter semantics, so this lands at the schema-backed baseline.

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+resource ('Check voucher status for this merchant'), which is enough for an agent to separate it from mutation siblings like use_voucher or create_gift_certificate. It stops short of explicitly naming the alternative sibling to use when the goal is redemption rather than status inspection.

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 is implied by the verb 'check' and the identifier requirement, but there is no explicit when-to-use/when-not-to-use guidance, e.g. status check versus use_voucher. The anyOf identifier rule is stated, which is the only concrete invocation guidance present.

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