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

Annotations provide no hints (all false), so the description bears the full burden. It discloses that the tool can apply or detach a voucher and that it is a paid feature, but does not mention side effects such as reversibility, impact on the booking, or error conditions. For a mutation tool with zero annotation coverage, this is a moderate but incomplete disclosure.

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 two sentences, front-loaded with the primary action and followed by the detach condition and paid-feature note. There is no fluff or repetition; every clause contributes to understanding the tool's purpose.

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 relatively simple mutation with 3 parameters and no output schema, the description covers the core use cases: applying and detaching, with examples and a cost condition. It lacks explicit handling of error cases or return values, but those are not always required. The description is mostly complete for an agent to decide when and how to invoke it.

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%, so the schema already explains all parameters. The description adds some nuance with examples (voucher types) and reiterates the detach behavior for booking_id, but this is largely redundant with the schema. It does not provide additional meaning beyond what the schema offers, so the baseline of 3 is appropriate.

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 clearly states the action 'apply' and the resource 'voucher to a booking', with specific examples (BA companion voucher, Barclaycard upgrade voucher) that differentiate it from generic booking tools. It also distinguishes from sibling tools like add_voucher or delete_voucher by specifying it affects existing bookings. The mention of 'detach' further clarifies its dual purpose.

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 description implies when to use it: when you have a held voucher and want to attach it to a booking or detach it. It gives context with examples and notes it is a paid feature, which is a use condition. However, it does not explicitly compare to alternatives like add_voucher or list_my_vouchers, though the distinction is implied by the tool name and sibling set.

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