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

With no annotations provided, the description carries the full behavioral disclosure burden. It clearly states that the tool returns a Stripe Checkout URL rather than directly charging, and that credits land only after payment completes, which is an important asynchronous behavior. It does not mention failure modes or whether the checkout URL expires, but the core transaction flow is adequately transparent.

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 dense but efficient, front-loading the main verb and resource before embedding the warning about the alternative URL. The parenthetical and rate/range details are relevant rather than filler, though the sentence structure is a bit run-on. Overall, every 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?

The tool has no output schema and no annotations, so the description must provide the return shape and behavioral expectations, which it does by stating the Stripe Checkout URL and the delayed credit settlement. The parameters are fully covered by the schema, and the description adds enough context for correct invocation. Minor gaps like checkout URL expiration or what happens on payment failure are not addressed, but they are not critical for basic use.

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 input schema already covers both parameters with 100% coverage, so the baseline is 3. The description adds meaningful context beyond the schema by explaining the conversion rate ($1 = 100 AGC) and the allowed purchase range ($1–$500), which helps an agent understand the value semantics of usdCents. It also clarifies the expected outcome, linking the payment to the credit balance.

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 opens with a specific verb and resource: 'Buy board AGC via Stripe,' making the tool's core function immediately clear. It also distinguishes itself from the public lab cash face by naming the alternative URL, which removes ambiguity. An agent can understand what this tool does and how it differs from other credit-related operations like spend_credits or transfer_credits.

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 says this is NOT the public lab cash face and provides the alternative URL, giving a clear exclusion criterion. It also explains the operational flow: the tool returns a Stripe Checkout URL, which should be opened or handed to an operator, and credits arrive only after payment completes. This is actionable guidance for when and how to use the tool.

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