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

Goes beyond annotations by explaining that the claim alone grants nothing until ownership is proven, and that it returns DNS records for verification. This contextualizes the non-idempotent and non-read-only nature without contradicting the annotations.

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 slightly verbose but every sentence carries essential information: purpose, consequence, workflow, and parameter timing. It is well-structured and free of fluff, though the multi-clause sentences could be tightened.

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 description covers the core workflow (claim, present records, verify) and references update_custom_domain for later configuration. It does not detail the output schema shape beyond dns_records, but that is provided separately, so the context is sufficient.

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 schema already covers all 4 parameters with detailed descriptions, so the baseline is 3. The description adds value by noting that slug_prefix and root_endpoint are typically set later, which clarifies their optional usage in this specific call.

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?

Clearly states the action (claim a custom hostname and generate DNS challenge) and differentiates from related tools like verify_custom_domain and update_custom_domain. It specifies the primary output (two DNS records) and the provisional nature of the claim.

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?

Explicitly instructs to present DNS records to the human, wait for them to be added, and then call verify_custom_domain. Also notes that slug_prefix/root_endpoint are usually set later with update_custom_domain, providing clear guidance on when to use alternatives.

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