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

The description adds real value beyond the annotations: it discloses that the call mutates state ('advances it as far as it currently can') and describes the three possible outcomes (still validating, certificate issued, active). But 'safe to call repeatedly' largely restates idempotentHint=true, so the behavioral content is partially duplicative; it also omits auth/prerequisite requirements for the site.

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 sentences, front-loaded with the action, followed by the enumerated return states. Every clause carries information and nothing is padded.

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?

For a one-param, no-output-schema tool whose annotations already cover safety and idempotency, the description is nearly sufficient: it explains the lifecycle states an agent will see. The remaining gap is the unexplained siteId and the relationship to set_custom_domain.

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 description coverage is 0% for the single required siteId parameter, and the description never mentions what siteId refers to or where it comes from. With the schema providing no documentation, the description was the only place to compensate, and it doesn't.

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 states a specific verb (re-checks and advances) and resource (a pending custom domain request), and explicitly frames it as re-checking a pending request, which separates it from the setup/removal siblings in spirit. However, it never names set_custom_domain or remove_custom_domain as the alternatives, so the differentiation is implicit rather than explicit.

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?

'Re-checks a pending custom domain request' and 'Safe to call repeatedly' give a clear condition for use (a request that is already pending) plus polling guidance. It stops short of explicitly saying to use set_custom_domain to create the request first or remove_custom_domain to tear it down, so it lacks named alternatives.

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