Create Domain

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

With no annotations, the description carries the full transparency burden. It goes beyond a simple 'creates' statement by disclosing the critical behavioral requirement: 'You MUST display the DNS records to the user so they can set them up.' This is a concrete, actionable side effect that the agent must handle. However, it does not disclose other potential behaviors (e.g., rate limits, irreversibility), so a 4 is appropriate.

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 two sentences, front-loaded with the primary action, and every word earns its place. It efficiently communicates purpose, output, and a critical mandatory action without redundancy.

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?

Given 8 parameters (one required, nested objects) and no output schema, the description provides a complete enough picture: it explains what the tool does, what it returns (DNS records), and what the agent must do with them. It does not explain the exact structure of the DNS records, but that is beyond the necessary remit and the key usage context is covered.

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 has 100% parameter description coverage, including details about defaults and meanings (e.g., TLS modes, region enums). The description adds no parameter-specific information beyond what the schema already provides. Per the rubric, baseline 3 is appropriate when schema does the heavy lifting.

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 clearly states the verb+resource: 'Create a new domain in Resend.' It also mentions the unique output (DNS records for verification), which distinguishes it from sibling tools like get-domain, update-domain, or verify-domain. This makes the tool's purpose unambiguous.

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 provides clear context for when to use this tool: when creating a new domain and needing DNS records for verification. It implies a workflow (create domain → configure DNS → verify), but does not explicitly name alternatives or state when not to use it. The mandatory instruction to display DNS records gives practical usage guidance.

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