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

The description discloses critical behavioral traits beyond annotations: nothing is credited until payment, the balance is credited exactly once by whichever component sees the payment first, and the operation is not idempotent (idempotentHint=false) without saying so directly. It also notes the live-only restriction. This adds valuable context beyond the annotations and schema.

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 purpose, then constraints, then the follow-up action. Every sentence carries meaningful information without fluff. It is dense but efficient, leaving no unnecessary words.

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 an output schema available, the description does not need to detail return values. It covers the essential flow: creation, handoff, follow-up with check_topup, and the single-credit guarantee. For a tool of this complexity, nothing an agent needs to invoke it correctly is missing.

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?

The schema already provides detailed descriptions for both apiKey (including prefix examples and source) and amountCents (including minimum and format). The description adds the dollar range $4.99–$1,000.00 and reiterates the live-account restriction, which is helpful but partially redundant. Given 100% schema coverage, the description adds a modest amount of extra context, so a 4 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 verb ('Creates a Stripe Checkout link') and the resource ('for a PERSON to pay with a card'), and distinguishes it from siblings by focusing on link creation rather than status checking (e.g., check_topup). It also mentions the key output 'checkoutUrl' to hand to the user.

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 explicitly specifies when to use it ('Live accounts only'), the allowed amount range, and the immediate next step ('Then call check_topup with the sessionId until credited is true'). It also explains the race condition for crediting, which guides correct usage. No alternatives are mentioned, but the workflow is unambiguous.

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