register_domain

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

Adds critical context beyond annotations: 'Spends account credit,' cost mismatch rejection, idempotency details (24-hour retries), and registration limitations. Annotations indicate idempotentHint=true and openWorldHint=true, which the description corroborates and enriches.

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?

Single paragraph with no fluff. Uses bold for key warning ('Spends account credit'). Information is logically ordered: warning, action, parameter constraint, workflow, idempotency, limitations, prerequisites. Every sentence adds value.

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?

Covers most practical concerns: prerequisite checks, idempotency, domain limitations. Lacks description of return value (no output schema), but this is a payment tool where response is likely standard. Minor gap for full completeness.

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% with detailed parameter descriptions. The description adds workflow context (check_domain first, years multiplier) but does not significantly enhance semantic understanding beyond what the schema provides. Baseline 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 uses a specific verb ('Registers') and resource ('domain on the authenticated Porkbun account'), clearly distinguishing from sibling tools like check_domain (checking availability) and renew_domain (renewing an existing domain).

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?

Explicit workflow: call check_domain first, confirm with user, then call this. States when NOT to use (premium domains, .uk, etc.) and prerequisites (verified email/phone, prior registration). Provides clear guidance on idempotency and retries.

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