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

Adds real context beyond the annotations: it has a serving side effect (site starts serving), issues certificates asynchronously within a minute or two, and returns a per-record remediation list on failure. The re-check note reinforces idempotentHint with practical meaning. It does not spell out whether the domain must be the only one affected or what happens to existing traffic during propagation, so not quite a 5.

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?

Front-loads the verification-and-serve behavior, then failure semantics, then timing/retry notes — each clause carries information. It is a dense run-on sentence where a small amount of structure would improve scannability, which keeps it below a 5.

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 prerequisite, side effects, failure output shape, propagation latency and retry safety, which is enough for an agent to call it correctly; return values need not be explained because an output schema exists. Only the comparison against DNS-inspection alternatives is missing.

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 100%, so both parameters are already documented, including that recordId comes from add_custom_domain. The description repeats the add_custom_domain linkage but contributes nothing new about the parameter values or formats; baseline 3 applies.

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?

States a specific verb and resource ('check the records ... and, when both are right, start serving the site on that domain') and anchors itself as the step after add_custom_domain. The agent can distinguish it from siblings like check_domain_availability, list_dns_records, add_custom_domain and verify_forms_sender_domain without reading the schema.

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?

Makes the prerequisite explicit ('the records from add_custom_domain', title says step 2 of 2) and gives retry guidance ('calling it again on a verified domain is a harmless re-check'). It doesn't address alternative situations, e.g. when to inspect DNS with list_dns_records instead, or when it's premature to call this.

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