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

Annotations declare readOnly/openWorld/idempotent/non-destructive, and the description adds substantial context beyond them: availability comes from the registry's RDAP, the quote is signed and one-year, and critically it discloses that this is a demo seller where prices are illustrative and register/renew are refused with demo_mode.

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?

Two dense sentences with zero filler; the core action and return values are front-loaded, and the demo-mode caveat is placed last where it belongs as a qualifier rather than the headline.

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?

Even without an output schema, the description enumerates the returned quote components (supplier cost, fixed markup, total in USDC) and explains the availability source and demo limitation. An agent has everything needed to call and interpret the result.

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 there is a single parameter whose format (exact registrable domain, e.g. example.com) is fully documented in the schema. The description adds no syntax or format detail beyond that, so the baseline 3 applies.

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 specific verbs (check availability, get a quote) and the exact resource scope (.com, .net, .org). It also names the concrete payload returned (supplier cost, markup, total in USDC), so an agent knows precisely what this tool produces.

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?

Clearly indicates the context (checking an exact registrable domain and pricing it) and adds the key exclusion that availability 'is not a reservation', which prevents an agent from treating a positive result as a hold. No alternatives exist since there are no sibling tools, so a 4 is appropriate.

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