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

With no annotations provided, the description carries the full burden of behavioral disclosure. It clearly communicates a read-only listing behavior and specifies the returned information, which is useful, but it omits details like whether pagination, ordering, or only-verified-domains filtering apply. The description is adequate but not deeply transparent.

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 that states the action, the object, scope, and key output fields without filler. Every phrase 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 is nearly complete: it names the main returned attributes (verification state and remaining allowance). It could be slightly richer about response format or relationship to other limit-related tools, but nothing essential is missing for a 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?

The tool has zero parameters and 100% schema coverage, so the schema already fully documents the input contract. The description adds no parameter-specific meaning, but none is needed; the zero-parameter baseline of 4 applies here.

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 uses a specific verb ('List') with a clear resource ('sending domains') and scope ('on this account'), immediately distinguishing it from siblings like list_messages and get_sending_limits. It also specifies what is returned: verification state and remaining sending allowance, leaving no ambiguity about the tool's function.

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 when to use it: when the agent needs domain-level verification state or remaining allowance information. However, it offers no explicit when-not-to-use guidance or mention of alternatives such as get_sending_limits, which might be relevant if account-level limits are needed.

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