list_available_domains

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

With no annotations, the description carries the burden of making behavior clear. 'List' communicates a read-only operation, and 'verified custom domains' explains an important eligibility constraint. It does not cover pagination or return format, but for a zero-parameter list operation this is sufficient transparency.

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 economical sentence that leads with the action and resource, then adds only the clarifying eligible-domain detail. Every word adds value; nothing is redundant or vague.

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?

For a simple, parameterless list tool, the description fully explains what is returned and the conditions under which a domain appears. It omits only minor details like ordering or whether empty lists are possible, which are not critical for correct invocation.

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?

There are no parameters, so there is no parameter semantics for the description to add. The zero-parameter baseline of 4 applies; the description correctly focuses on what the tool returns rather than on 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?

States the specific verb 'List' and the ressource 'domains the user can create aliases on'. The parenthetical ('system domains + their verified custom domains') tightens the scope and clearly distinguishes it from sibling list tools like list_aliases or list_destinations.

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 clearly signals that this is the tool to call when the user needs to know which domains are eligible for alias creation. It does not explicitly name alternatives or say 'use before create_alias', but the context is strong enough for an agent to route correctly.

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