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

Annotations declare this is a destructive, open-world write, and the description adds context beyond them: project-administrator authorization is required, the backend performs DNS validation and SSL enablement automatically so no Verify click or validate API call is needed, and the caller is told to present DNS records verbatim. These are non-obvious operational facts not derivable from the schema or 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-loads the action and return value in the first sentence, then layers prerequisites, idempotency, parameter guidance, and backend behavior in short declarative statements. No sentence is redundant with the schema or annotations.

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?

Although there is no output schema, the description explains what comes back (DNS records to present exactly) and what happens afterward (automatic DNS checking and SSL). Combined with the auth requirement and idempotency contract, an agent has everything needed to call this correctly on first attempt.

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%, so the description carries the full burden and does so for the two non-obvious parameters: idempotency_key (unique per attempt, reused for retries, regenerated after cancel/re-add) and use_www (root domains default to www as primary). domain and project_id are left unexplained but are self-evident from their names.

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 ('Connect the owner's custom hostname') plus the side effect of returning DNS records. It is clearly distinguishable from the sibling get_custom_domain, which is explicitly named as a prerequisite rather than an equivalent.

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 sequencing ('Call get_custom_domain first'), an exclusion ('Do not replace an existing domain implicitly'), and the condition selecting the use_www variant ('only when the owner explicitly requests the root hostname as primary'). It also routes retries via the idempotency key, leaving little to inference.

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