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

Annotations already cover read-only/open-world/non-idempotent, and the description goes well beyond them: per-call price, USDC wallet charging, budget-cap enforcement, the fact that "not registered" results still cost money, and an explicit third-party-data/not-instructions warning. That is exactly the extra behavioral context an agent needs before spending money.

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?

Four short sentences, front-loaded with purpose, then pricing, payment mechanics, and a safety caveat. Every sentence carries information; only the price/product aside is slightly redundant with the payment sentence.

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 does not describe the shape of returned registration fields (registrar, dates, statuses) or how a "not registered" answer is surfaced, which is a modest gap. Cost, budget, and data-trust context are otherwise complete for a simple two-parameter lookup.

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%, with both domain and confirm_over_cap fully documented in the schema, so baseline is 3. The description adds no parameter-level detail (no domain format, no note about turning on confirm_over_cap) beyond what the schema states.

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+resource (domain registration data) and the protocol (RDAP), which is enough to separate it from generic lookups like company_lookup or patent_lookup. It stops short of explicitly naming a sibling alternative, so it is clear but not maximally differentiated.

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 clearly frames cost and budget gating ("only within the budget caps"), which is real usage guidance, but it never says when to prefer this over other lookup tools or when the lookup is inappropriate. Usage context is implied rather than stated.

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