List private domains

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

With no annotations, the description carries the full burden, but it does add a genuine behavioral fact: mail to a private domain is visible only to the account. It still omits read-only confirmation, pagination behavior, and what the account scope actually means for results.

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?

Two sentences, no filler, with the primary action front-loaded and the usage hint following immediately. Every clause earns its place.

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 zero-parameter list tool with no output schema, the description covers what is listed, the visibility semantics, and the follow-up call. It could state the return shape (e.g. a list of domain names) explicitly, but nothing critical is missing.

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 the baseline is 4. The description goes slightly beyond by naming the downstream parameter slot (`domain` on create_test_address) where a returned value is consumed, which helps an agent chain calls.

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 tied to the Mailsac account ('List the private domains on this Mailsac account'), which is unambiguous about what is returned. It does not differentiate against sibling list tools (list_emails, list_domains vs them) beyond naming create_test_address as a downstream consumer.

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 implies the use case by explaining that a listed domain can be passed as `domain` to create_test_address, which is a helpful workflow pointer. However, it never states when to call this tool versus alternatives such as list_emails, nor any prerequisites or exclusions.

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