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

Annotations already declare readOnlyHint=false, destructiveHint=false, and openWorldHint=false, so the description need only add context beyond that — and it adds none. It doesn't mention that the domain stays unverified until DNS records are confirmed, what happens if the domain is already attached, or whether the operation is idempotent. The openWorldHint=false annotation is also worth noting: registering an external domain name arguably reaches outside the closed system, so the description could have clarified the actual scope.

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?

A single front-loaded sentence with zero filler, which is appropriately sized. It is arguably over-terse for an operation that appears to have a multi-step lifecycle, but it wastes no words.

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?

This is a mutation with no output schema and minimal annotations, so the description carries real explanatory burden. It omits the likely verification requirement, doesn't state what the caller gets back, and gives no failure or conflict behavior — an agent cannot confidently complete the workflow from this alone.

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% with only two parameters, both required and both documented in the schema (domain name with example format, deployment UUID). The description adds no format or constraint detail beyond that, so the 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: 'Add a custom domain to a deployment.' This is clear and action-oriented. It does not, however, distinguish itself from adjacent siblings like nexusai_domains_verify or nexusai_domains_remove, so differentiation comes from the tool name rather than the description.

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?

The description gives no when-to-use context, no prerequisites (e.g. the domain must already point at the platform's DNS), and no mention of the follow-up verification step implied by the sibling nexusai_domains_verify. The agent must infer the workflow entirely.

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