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

Beyond the annotations, the description discloses that a webhook fulfills the grant, which is important non-obvious behavior: the grant is not immediate. This aligns with readOnlyHint=false and does not contradict the annotations, though it could say a bit more about checkout flow details.

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 short and front-loaded: it states the action, the resource, the payment-rail context, and the fulfillment caveat in two sentences. Every sentence carries information an agent needs.

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 full parameter coverage in the schema and an output schema present, the description covers the essential context: when to use it, what it creates, and how fulfillment happens. It could also transparently mention that the returned checkout URL is intended for the buyer, but that is mostly covered by the overall tool behavior.

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?

Since schema description coverage is 100%, the parameters are already fully documented. The description only restates the purpose choices ('Pro tier or tool credits') and does not add new parameter-level semantics such as required combinations or format constraints.

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 uses a specific verb and resource, 'Create a Stripe Checkout Session', and immediately names its two purposes: Pro tier or tool credits. The phrase 'fiat rail' clearly distinguishes it from USDC-based payment siblings, so an agent can tell what this tool does.

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 gives an explicit usage condition: use when the buyer pays by card instead of USDC. It also clarifies that fulfillment happens via webhook. It doesn't explicitly name a sibling tool for the USDC case, so the comparative routing is implied rather than fully spelled out.

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