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

With no annotations provided, the description carries the full burden. It discloses the pricing formula ('200 service tokens plus the domain registration price'), dependency on billing plan, and the tool's own cost ('Cost = 5 tokens'). This goes beyond a simple read-only hint, though it does not explicitly state 'no side effects' or describe error conditions.

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?

The description is front-loaded with the core purpose and remains brief. Each sentence adds value, including the cost formula and the 'Use before domains.register' guidance. The final 'Cost = 5 tokens.' is a distinct tool-cost disclosure, though it could be mistaken for the quoted cost without careful reading.

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 tool has an output schema and fully documented parameters, so the description does not need to explain return values. It explains the cost structure, usage timing, and external dependency (billing plan), making it complete for a simple quote tool. Minor gaps include lack of edge-case handling (e.g., invalid domain), but the output schema likely covers those.

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?

The input schema already includes descriptions for both parameters (domain and years) with constraints, achieving 100% coverage. The description adds the cost formula context but does not substantially clarify parameter semantics beyond what the schema provides. Baseline of 3 is appropriate.

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 begins with a specific verb and resource: 'Quote registration cost in tokens for one domain and year count.' It clearly distinguishes this from sibling tools like domains.renewal_quote by explicitly saying 'registration cost' and 'Use before domains.register.'

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 explicitly states when to use this tool: 'Use before domains.register.' This provides a clear usage context and names a direct alternative (domains.register) in the sibling list. The phrase 'for one domain and year count' further clarifies scoping, though it does not explicitly exclude renewal quotes.

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