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

Annotations already declare non-read-only, non-destructive, non-idempotent, closed-world, and the description adds the crucial non-obvious state trait: the mailer is created inactive, so nothing sends until another call. It doesn't cover auth/permission needs or rate limits, so not a 5.

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?

Three short sentences, front-loaded with the create action, then the inactive-state consequence, then the template-editing follow-up. No filler or restated parameter lists.

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?

Output schema exists so return values needn't be explained, params are fully documented in schema, and the description supplies the lifecycle state (inactive) plus next-step tools an agent needs to complete a mailer workflow. Nothing essential 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 each of the 14 params is documented inline (kind immutability, event_id source, group_ids conditional on access_level, feature_selection_id constraints), so the schema does the heavy lifting. The description adds only the email_template_id editing pointer, which refers to a returned field rather than a create parameter, so baseline 3 applies.

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+resource ('Create a new email mailer') with scope ('for the provided event'), and explicitly names the sibling tools this is not (activate_mailer, schedule_mailer, update_email_template). An agent can tell it apart from duplicate_mailer or update_mailer without opening any 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?

Explicitly states the when: create here, then use activate_mailer to start sending or schedule_mailer for later delivery, and update_email_template (with email_template_id) to change body/html. This is direct routing to the correct alternatives, not inference.

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