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

Annotations already flag readOnly, idempotent, non-destructive, open-world, and the description reinforces the most consequential fact: no charge occurs and the agent cannot take payment. It goes further than annotations by disclosing downstream effects — after payment the domain is registered and auto-connected to the site, usually live within minutes, with a user notification. That is real behavioral context an agent cannot infer from the hints.

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?

Front-loaded with the action and the returned artifact, then the required agent behavior (send the link), then the no-charge guarantee. Every sentence carries a distinct, decision-relevant fact with no 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?

With no output schema, the description correctly names the key return value (purchase_link) and the quote contents. It also covers what happens after the user pays, closing the loop for a tool that is the first half of a two-step purchase flow.

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%, so the schema already documents domain, site_id, years, and user_goal. The description reinforces the years term values and the exact-match provenance of domain, but that reproduces what the schema text already states; site_id and user_goal get no added meaning. Baseline 3 for a fully documented schema.

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 ("Prepare the purchase of a domain") and enumerates exactly what the call does: re-checks availability, quotes the term with renewal price, and returns purchase_link. It anchors itself to the sibling that produces its input (search_domains_to_buy), so an agent can place it in the domain workflow without opening the 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?

Clear when-to-use chain: after search_domains_to_buy, then hand purchase_link to the user who confirms contact details and pays. It also sets a boundary ("Nothing is charged by this call and you cannot take payment"). The gap is that siblings claim_domain and verify_domain are never mentioned, so the agent gets no explicit routing against those adjacent steps.

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