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

Annotations already declare readOnlyHint=true and destructiveHint=false, covering safety. The description adds meaningful behavioral context by explaining the different return types for single vs batch jobs ('final verdict once the mailbox probe completes' vs 'progress + a result-mix summary'). This goes beyond the annotations and clarifies what to expect in the response, though it does not discuss error handling or timing details.

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?

The description is two concise sentences, front-loaded with the action and resource, and immediately elaborates on expected behavior. Every sentence earns its place, with no fluff or repetition of schema information.

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 simple lookup tool with one parameter and no output schema, the description is complete. It explains the purpose, the input source, and the output behavior for both single and batch cases. The rich sibling context and annotations further reduce ambiguity, making this sufficiently complete for an agent to use correctly.

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 the schema already describes job_id as 'The job_id returned by a verify tool.' The description repeats this information, adding little new value. It reinforces the source but does not provide additional syntax, format, or usage details beyond the schema, so baseline 3 is 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?

The description clearly states the tool 'Look up the status and result of a verification you started' with a specific resource (job_id). It distinguishes itself from sibling verification-starting tools by referencing job_id from verify_email/verify_emails and explaining single vs batch behavior, making its purpose 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 implies usage after starting a verification by referencing 'verification you started' and job_id from verify tools. It does not explicitly name alternatives or exclusions, but the context is clear enough that an agent would know to use this for retrieving results, not for initiating checks. A minor gap is the lack of explicit 'use this only after a verification has been started' guidance.

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