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

Annotations already cover safety (readOnly, idempotent, non-destructive, closed-world), yet the description still adds non-obvious semantics: enabled vs planned is not a chargeability signal, and silent fallback to Stripe Checkout is prohibited. That is real behavioral context beyond the structured fields.

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?

Three sentences, all load-bearing, with the operational imperative front-loaded before the field inventory and the caveats. No restatement of the title or name.

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, so the description carries the return-shape burden — and it does: it enumerates status, environment (live/sandbox/offline_sandbox), required customer interaction, supported buyer modes, and unavailable reason. Nothing essential for correct invocation 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?

Zero parameters, so there is nothing for the description to disambiguate and the baseline applies. It correctly omits parameter talk rather than padding, though it also doesn't state that no inputs are needed (e.g., environment scoping comes from the caller's context).

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 ('Read the payment-method capability matrix') and explicitly separates itself from the write-path sibling by naming purchase and create_checkout-adjacent behavior. An agent can distinguish discovery from action without opening a schema.

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 explicit ordering guidance ('BEFORE invoking purchase'), plus when-not reasoning: a planned method may not charge, and autonomous flows must not silently fall back to human Stripe Checkout. This is exactly the when/when-not/alternative coverage the dimension asks for.

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