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

Goes well beyond the annotations: annotations only say non-readOnly, non-idempotent, openWorld. The description adds that this consumes paid credits, that confirm:true gates the spend, that the platform does not retry, and that the outcome is asynchronous and must be polled. Those are exactly the traits an agent needs to avoid duplicate charged submissions.

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?

Four short sentences, each carrying distinct operational information (scope, cost/gate, retry policy, next step and recovery). The critical cost/confirm constraint is front-loaded in sentence two with zero filler.

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?

No output schema exists, yet the description explains what the call returns conceptually (a verification ID) and points to the sibling that materializes it, plus how to poll and how to recover from a lost response. For a two-parameter async mutation, an agent has everything needed to invoke it correctly and safely.

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 0%, so the description must compensate; it does for 'confirm' by explaining that it gates credit spend, which the bare boolean default=false would not convey. 'email' is largely self-documenting from the format/pattern constraint, and the description reinforces single-email scope ('Submit one email'), but it doesn't explain what happens if confirm is omitted or the exact rejection behavior. Strong but not exhaustive.

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 and resource ('Submit one email for asynchronous verification') and immediately distinguishes itself from the sibling that reads the outcome ('Read the returned verification ID with mailercheck_verification_result'). An agent can tell it starts the job rather than fetches the result 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?

Gives explicit operational conditions: confirm:true is required, credits are spent, the call is never retried, polls should be spaced out, and lost responses should be checked in MailerCheck before resubmitting. It names the follow-up alternative (mailercheck_verification_result) and the recovery path, leaving little to inference.

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