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

Annotations only say readOnlyHint=false and idempotentHint=true; the description supplies the crucial reason why a 'get' is not read-only, spelling out the pending_validation → provisioning → pending_dns → active state machine and warning 'Nothing advances on its own.' It also discloses the response payload (dnsRecords with done flags, instructions), which is real behavioral context beyond 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?

Front-loaded with purpose, then lifecycle, then response shape — a sensible order. The lifecycle chain is dense but each stage carries actionable information ('create the routing CNAME from the domain to `target`'), so little is wasted, though it runs longer than strictly necessary.

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?

With no output schema, the description carries the burden of explaining returns and does so ('always carries dnsRecords... and instructions saying what to do next'). For a zero-param, state-advancing tool, an agent has everything needed to call it at the right moment and interpret the result.

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 tool takes zero parameters, so per the rubric the baseline is 4; there is nothing for the description to disambiguate. It correctly avoids inventing parameter details that don't exist.

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+resource ('Get this tenant's custom (alias) domain') and adds the non-obvious scope that the call also advances setup. This clearly separates it from set_custom_domain and remove_custom_domain in the sibling list.

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?

Gives explicit trigger conditions: 'Use it to check progress after creating a DNS record' and 'call get_custom_domain after each DNS change to move it along.' It does not explicitly name set_custom_domain/remove_custom_domain as the alternatives to pick instead, so it falls just short of a 5.

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