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

Annotations already declare destructiveHint=true and non-idempotent, so the bar is lower; the description still adds real value by disclosing that activation queues delivery to actual recipients and is irreversible. It stops short of noting permissions, whether the mailer can be deactivated afterward, or what a partially-queued state means.

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 short sentences, zero waste, with the core action first and the risk warning immediately after. Nothing is repeated or padded.

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?

With an output schema and annotations covering the safety profile, the description supplies the key missing piece: that this triggers real sending and is irreversible. The remaining gap is routing guidance relative to send_test_mailer/deactivate_mailer, which an agent would still have to infer.

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 coverage is 100% and both required parameters (event_id, mailer_id) carry their own descriptions, so the schema does the heavy lifting. The description adds no extra meaning about parameter formats or constraints, making the baseline 3 appropriate.

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 ("Activate a mailer") and the second sentence clarifies the effect (queues sending to real recipients). It implicitly distinguishes itself from send_test_mailer by emphasizing real recipients, but never names the sibling, so differentiation is only partial.

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 this is the final, production-sending step for reminder/promotion/certificate mailers, which is useful context. However, it gives no explicit guidance on when to use it versus send_test_mailer, deactivate_mailer, or publish-style siblings, and no preconditions (e.g., preview or test first) are stated.

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