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

Annotations already declare read-only, idempotent, and non-destructive behavior. The description adds meaningful context beyond annotations by explaining what the returned entries represent (SMTP servers vs. verified sending domains) and how the output should be consumed. This enriches the agent's understanding of the result without contradicting the hints.

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 carry exactly the needed information: the scope, the semantic distinction between server types, and the actionable next step. It is front-loaded with the resource and purpose, with no filler or repetition.

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 parameterless, read-only, idempotent list tool, this description is complete. It explains what is listed, why it is relevant, and how to use a returned value. The absence of an output schema is mitigated by the explanation of server types and the guidance about `server_id`.

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 the schema coverage is 100%, so the baseline of 4 applies. The description adds no parameter documentation because none is needed, but it does clarify the meaning of returned server types, which supports future parameter use via `server_id`.

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 states the tool lists email servers configured by teams in the dashboard and explains the practical purpose: use one as a form's notification sender. It also distinguishes the two server variants (`email_server` as SMTP, `premium_server` as verified domain), going well beyond the title and making the resource 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?

The description provides clear usage context: this tool is for obtaining email servers to use as form notification senders, and it explicitly instructs where the resulting id belongs (`self_email_notification.sender.server_id`). It doesn't name alternatives or exclusions, but there are no competing email-server-specific siblings, so the guidance is practically sufficient.

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