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

The description discloses meaningful behavior beyond readOnlyHint=true: the domain lands in the buyer's account, an account-claim email is sent after payment, and the returned pay_url is a real HTTP 402 challenge meant to be handed directly to an MPP pay tool. It also warns that the buyer_email must be the true end buyer because ownership follows that email. No contradiction with annotations exists.

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?

Every sentence earns its place: core purpose, sibling differentiation, usage conditions, buyer-email warning, and handling of the HTTP 402 pay_url are packed into a compact, front-loaded description. Despite covering ten parameters and complex behavior, it remains readable and free of filler.

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?

The description covers purpose, selection criteria, account-ownership consequences, parameter significance, and post-return handling of the pay_url. Since an output schema exists, there is no need to elaborate return values, and 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?

Schema coverage is 100%, so the baseline is 3, but the description adds valuable context: buyer_email must be the real end buyer because the account and domain belong to them, and the contact parameters collectively form the registrant WHOIS details. It further instructs the agent to pass the exact server-computed pay_url/price rather than estimating, which affects how returned values should be used.

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 opens with a specific verb-resource pair: get a real payable MPP URL to purchase an already-listed Atom marketplace domain without an OAuth connection. It explicitly distinguishes this from get_domain_register_pay_link_guest for fresh unlisted domains and from get_domain_purchase_pay_link for authenticated sessions, so an agent can disambiguate by description alone.

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 states exact usage conditions: use only when no authenticated Atom connection exists, otherwise prefer get_domain_purchase_pay_link; and only when MPP payment tools such as link-cli's mpp_pay are available. It also names the alternative for unlisted domains, leaving no ambiguity about when to choose this tool over siblings.

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