List sending domains

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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint, covering the safety profile. The description adds genuine context beyond that: the return contents (verification status and DNS records) and the prerequisite note that the project UUID is not derivable from the API key and must be pulled from the dashboard URL.

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?

Bold-labeled sections are front-loaded and each earns its place; the reader gets purpose, exclusion, return, and prerequisite at a glance. Mild redundancy with the schema on the projectId note keeps it just short of a 5.

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 read-only one-parameter list tool with annotations covering safety and no output schema, the definition supplies everything needed: purpose, alternative, when-to-use, return contents and the UUID prerequisite. Nothing an agent needs to call it correctly 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?

Schema description coverage is 100% and the single parameter is fully documented in-schema, so the baseline is 3. The description's note about the UUID not being derivable from the API key adds a small amount of meaning, but largely restates what the schema already says about locating it in the dashboard URL.

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 (list) and resource (project's sending domains) and explicitly includes the verification-status scope. It names the sibling it is not (plunk_verify_email), so an agent can distinguish it without opening either schema.

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?

Provides an explicit 'Not for' exclusion routing to plunk_verify_email and a 'Use when' condition (before sending, to confirm the from address sits on a verified domain). When-to-use and the alternative are both spelled out.

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