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

Annotations already cover read-only, idempotent, and non-destructive behavior, but the description adds valuable context: Stripe transactionId/secretKey are returned as-is, GET does not create or refresh a PaymentIntent, servicesAttachable is live and not persisted, and creditLine is conditional on includeCreditBalance and account coverage.

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 markdown is front-loaded and well-structured with scannable sections. However, the Overview and 'What You Get' sections repeat return-shape and servicesAttachable details, making it slightly verbose for a two-parameter read tool.

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 still conveys the return shape, persistence semantics, payment-intent behavior, and optional creditLine behavior. Annotations cover safety, so the combination is complete enough for correct invocation.

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 both parameters. The description adds useful meaning by saying prebookId comes from POST /flights/prebooks and clarifying that includeCreditBalance returns a live remaining-credit snapshot when the account can cover the prebook price.

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 ('Retrieve') and resource ('flight checkout session (prebook)') by ID, including ancillary services and live catalog scope. It distinguishes the read-only GET from POST create/attach siblings by noting that GET does not create or refresh a PaymentIntent.

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?

Has a dedicated 'When to Use' section naming four concrete scenarios: resume checkout, confirm attached ancillaries, reuse payment intent, and include credit balance. It also contrasts with POST behavior and explains where prebookId comes from.

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