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

Goes well beyond the readOnly/non-destructive annotations: it discloses that nothing is charged, the link is not pre-authenticated, the user must already be logged into atom.com, and that sold or make-offer listings surface 'not_found'/'not_for_sale'. It also names the return payload and expiry, which the annotations cannot express.

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?

Purpose and the sibling alternative are front-loaded, and every paragraph (priority ladder, auth caveat, error states, returns) carries distinct operational value. It is longer than typical, but the sectioned structure keeps it navigable rather than padded.

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?

Given an output schema already exists, the description still adds the failure modes, the authentication precondition, and the explicit user-facing instructions ('present the price and the checkout link'). An agent has everything needed to invoke it and hand the result to a user correctly.

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 both parameters are documented there, including the default for term_years. The description adds no extra meaning for 'domain' or 'term_years' beyond the pre-filled-link framing, so baseline 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?

States a specific verb and artefact ('Generate a pre-filled Atom checkout URL') and immediately contrasts it with the sibling that does the actual purchase ('no-debit alternative to register_domain'). An agent can distinguish it from register_domain and the various pay-link siblings 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?

Explicit when-to-use and when-not-to-use: only for buying a premium/marketplace domain, only after register_domain balance is insufficient AND the priority-2 pay-link path is unavailable, with a direct statement that no equivalent exists for fresh registrations or AI Tokens. Alternatives are named and ordered, leaving nothing to inference.

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