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

The annotations already establish a safe, read-only operation, while the description adds account scope and the inclusion of a daily remaining-sends value. It does not clarify whether that value is account-wide or associated with individual domains or addresses, nor does it describe freshness or other result behavior.

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 single compact statement is front-loaded with the primary resource and adds only two relevant result details. There is no redundant or unnecessary wording.

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, read-only listing tool, the description identifies the scope and principal returned information well enough to support invocation. Because there is no output schema, the ambiguous placement and meaning of 'remaining sends today' is a noticeable but limited gap.

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 input parameters to explain, so the baseline score of 4 applies. The description's account scope also makes clear that no domain or account identifier needs to be inferred or supplied.

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 account-scoped resources returned: sending domains, a managed GrowFast address, and remaining sends for the day. Although written as a noun phrase rather than an explicit verb, it communicates the tool's purpose well; it does not explicitly differentiate it from siblings.

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 implied for agents that need sending identities together with current daily sending capacity. There is no explicit guidance on when to use this tool, when another tool is preferable, or whether it is suitable when only allowance information is needed.

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