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

Goes well beyond the annotations: discloses the registered-account session requirement, the guest rejection path, that the booking is confirmed automatically by webhook once payment succeeds, and that a `url` plus `sessionId` are returned for sharing with the guest. Annotations only say readOnly=false/destructive=false; the description supplies the real behavioral picture.

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?

Front-loaded with the action and the alternative rail, then prerequisites, then auth constraint, then return value. It is dense and every sentence carries information, though the all-caps session warning makes the middle block slightly harder to scan.

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 correctly states the return values (url, sessionId) and the downstream effect (webhook confirmation). The main gap is the undocumented `sessionToken` parameter, which the description implicitly contradicts by declaring guest sessions invalid here.

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%, so the schema already documents all five parameters; the description mainly restates required vs optional fields and the `preparedBookingId` origin already noted in the schema. It adds little new meaning and never addresses the `sessionToken` parameter, which sits awkwardly against the 'guest_login is REJECTED here' statement.

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 and resource ('Creates a hosted Stripe (credit-card) checkout link') and immediately frames it as an alternative rail to `create_checkout` (Revolut). An agent can distinguish it from the sibling without opening either 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?

Explicit when-to-use and when-not: 'Prefer `create_checkout` unless a Stripe card link is specifically needed' plus the hard condition that a `guest_login` session is rejected and guests must use `create_checkout` instead. It also names the upstream prerequisite `prepare_booking`.

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