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

Consistent with readOnlyHint=true and adds substantial context the annotations cannot convey: nothing is bought or ordered, names are not reserved until payment, unavailable names are dropped and listed, and a human must complete checkout with terms and withdrawal-waiver consent.

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 key non-purchase disclaimer and dense with useful information, though the parenthetical about .si mixing and per-ending pricing is slightly overstuffed for a description whose schema already lists the endings.

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?

No output schema exists, and the description still explains exactly what comes back (one checkout link plus a list of unavailable names) and what happens after payment, leaving no material gap for a zero-required-parameter tool.

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 baseline is 3; the description still adds the either/or selection rule between `domain` and `domains` and the combined-checkout semantics, which the schema does not state.

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 one or several domains ... in ONE checkout') and explicitly negates the obvious misreading ('This does NOT buy anything and creates no order'), which cleanly separates it from check_domain and start_renewal.

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?

Gives explicit selection rules ('Pass `domain` for one name or `domains` for several'), tells the agent what to do with the result ('Give the link to the user'), and names the follow-up tools (list_orders, get_order) with the condition for using them.

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