list_domains

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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered without the description. The only added context is the account-level scope ("connected to the account"), and nothing is said about result volume, pagination, or ordering for an open-world list, which is the one genuinely useful behavioral detail still missing.

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; the resource and its scope appear immediately. Nothing is repeated or padded.

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, annotation-covered list tool this is nearly sufficient; the agent knows exactly what is returned conceptually and that the call is a safe read. The only omission is whether results are paginated or complete, which matters because there is no output schema to fall back on.

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 there is no parameter semantics to explain; the schema is empty and fully covered. Baseline 4 applies with no gap the description could have filled.

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 gives a specific verb+resource ("List the custom domains") and scopes it to domains attached to the account, so an agent can tell it apart from alias, label, recipient, and rule listing siblings by the noun alone. It stops short of explicitly naming any sibling, but the resource noun is unambiguous.

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?

Usage is only implied: the enumerate-noun pattern makes clear this is the read path for domains, contrasting implicitly with create_domain/delete_domain. There is no explicit when-to-use, no note on whether a per-domain lookup alternative exists, and no stated preconditions.

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