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

The description goes well beyond the sparse annotations: it discloses that the card is saved automatically, that no charge is made, that it is setup mode only, and that the URL is one-time. This is precisely the behavioral context an agent needs to invoke the tool safely.

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 carry only relevant information: the returned artifact, the automatic side effect, the no-charge safety detail, and the agent's next action. No filler or repetition.

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 input parameters and no output schema, the description still tells the agent what field to expect, how to present it, that the flow is hosted, and who is allowed to use it. This is complete for the tool's complexity.

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 tool has zero parameters and schema description coverage is 100%, so there is no parameter information the description needs to add. The 0-parameter baseline of 4 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?

The description states the exact purpose: returns a one-time Stripe Checkout URL so the user can add a payment card. It clearly differentiates from payment_methods_list by describing an initiation/hosting action, not a listing action.

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?

It tells the agent exactly what to do with the result ('present the checkout_url to the user') and restricts to 'Buyer principals only.' It does not explicitly name an alternative tool, but the 'nothing else for the agent to do' instruction is strong usage guidance.

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