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

Annotations only cover the generic safety profile (openWorld, non-idempotent, non-destructive); the description adds real behavior — one-time session, credits land on the balance only after payment completes, poll GET /keys/me, free with no quota consumption, and the auth prerequisite. This is well beyond what the structured fields disclose.

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 core action and outcome, then prerequisites. The trailing parenthetical repeating the endpoint URL and 'free' is mild redundancy, but nearly every clause carries information.

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?

No output schema exists, and the description compensates by explaining what happens after payment and how to observe the result via GET /keys/me. An agent has everything needed to call it correctly and interpret the follow-up.

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% and the schema already explains the pack parameter with an example value and a pointer to credits_packs. The description's mention of 'credit pack' adds no 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?

States a specific verb and resource — creating a one-time Stripe Checkout Session for a credit pack — and scopes it to the calling live key's account. It is clearly distinguishable from credits_packs, which lists packs rather than creating a checkout.

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?

Gives strong usage context: it is what a 402 topUp.checkoutEndpoint points at, and it requires a connected account or a dv_sk_ key. It also defers pack selection to credits_packs, though it never states an explicit when-not condition.

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