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

Annotations already declare readOnly, idempotent, and non-destructive. The description adds meaningful behavioral context: the agent itself pays via an HTTP 402 challenge using the person's wallet credential, and no code is sent to the customer for paid bookings. It also clarifies the not_payable response for free bookings. This goes beyond annotations without contradicting them.

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 three sentences, concise and front-loaded with the trigger condition. It includes essential behavioral details (payment mechanism, free-booking alternative) without redundancy, so each sentence earns its place.

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?

Given the tool's complexity (payment flow) and that an output schema exists, the description covers the trigger, the return values, and the alternative for free bookings. It also explains the payment process. The output format is not detailed, but that is covered by the output schema, so nothing critical is missing for an agent to invoke it correctly.

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% for both parameters, and the description only reiterates that reservation_id comes from reserve_slot with payment.required = true, which is already in the schema description. No new semantics are added beyond what the schema provides, 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 states the specific purpose: for a reservation with payment.required = true, it returns the payment link, amount charged now, and balance due. It explicitly distinguishes this from confirm_booking by noting that free bookings (not_payable) should use confirm_booking instead. The condition is precise, so an agent can clearly identify when this tool applies.

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?

It gives explicit when-to-use guidance (reserve_slot returned payment.required = true) and when-not-to-use (free bookings answer not_payable), and names the alternative tool (confirm_booking). This is complete routing information with no ambiguity.

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