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

The description goes beyond the annotations by explaining the real-world side effect boundary: no charge occurs until a person completes checkout in a browser. It also names specific failure cases and the important instruction not to present the returned URL as a completed purchase. This is exactly the kind of behavioral nuance an agent needs.

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 tightly written, with the core action front-loaded and the critical payment caveat placed immediately after. Every sentence earns its place, including the error conditions, without unnecessary detail.

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?

For a checkout-link creation tool, the description covers what it returns, who should open it, the most important safety caveat, and the common failure conditions. Combined with the output schema and annotations, this gives an agent enough to invoke the tool correctly and interpret the result appropriately.

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%, and both parameters have meaningful schema descriptions. The tool description adds some context by mapping 'one listing' and 'one paid add-on' to the slug and product, but it does not need to compensate for missing schema documentation. Baseline of 3 is appropriate.

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 a specific action ('Create a Stripe checkout URL') and the exact resource scope: one paid add-on on one listing. It clearly distinguishes this tool from the sibling tools by focusing on purchase/checkout rather than lookup or submission.

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 makes the intended use clear: generate a checkout link for a human to open, and never treat this as a completed purchase. It also documents error conditions that tell the agent when the tool cannot be used. It does not explicitly name sibling alternatives, but the context is clear enough to avoid misselection.

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