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

The annotations already establish that this is a read-only, idempotent, non-destructive, closed-world operation. The description adds useful behavioral context by stating the scope is the workspace's Resend account and that the result indicates whether HelpWell uses each domain, though it does not discuss response format or ordering.

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?

The definition is a single compact sentence with no redundant text. The resource, reuse context, and alternative are all front-loaded.

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 usefully explains that the tool returns domains and whether HelpWell uses each. It could be richer about the exact fields returned for reuse decisions, but it is otherwise complete for a simple zero-parameter list tool.

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?

This tool takes no parameters, so there are no parameter semantics to explain. The baseline for a zero-parameter tool is 4, and the description does not need to compensate for undocumented inputs.

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 clearly identifies the resource as domains in the workspace's Resend account and adds that it reports whether HelpWell uses each. It distinguishes the tool from reuse_resend_domain and from adding a new domain, though it is phrased as a noun fragment rather than an explicit verb-led definition.

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?

It gives a clear use context: check existing domains so one can be reused with reuse_resend_domain instead of added again. The alternative reuse_resend_domain is named explicitly, but there is no explicit when-not-to-use guidance or mention of related add/check domain tools.

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