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

Annotations already declare the mutation/read-write profile, and the description adds genuinely useful behavior: it returns a checkout URL that must be opened, credits are only applied after Stripe reports the session paid, and an API error is returned when Stripe is not configured. That async-settlement and failure-mode context goes beyond what the annotations convey, though it stops short of covering repeat invocations or session expiry.

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 underlying route, and the operational notes (open the URL, credits applied post-payment) each earn their space. There is mild redundancy in restating the credits range already present in the schema.

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 compensates by explaining the return value (the checkout URL) and its handling. It also covers the Stripe-not-configured error path and the delayed credit application, leaving only minor gaps around wallet prerequisites and idempotency on repeat calls.

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 description coverage is 100%, so all three parameters are already documented, including the 500–100000 range and the 1 credit = $0.01 conversion. The description largely restates the credits bounds and adds little syntax or format detail beyond the schema, so the baseline 3 applies.

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?

Names a specific verb and resource: starting a Stripe Checkout credit top-up, and anchors it to the underlying POST /v1/wallets/:id/checkout route so the agent knows exactly what is invoked. It does not, however, distinguish itself from the sibling `purchase`, which an agent could plausibly confuse with this tool.

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?

Usage is only implied: the agent can infer this is the way to buy credits via Stripe's hosted page, but there is no explicit when-to-use statement and no guidance on choosing between this and the sibling `purchase`. No prerequisites (e.g., needing a valid wallet) or exclusions are given.

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