Verify email

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

Adds materially beyond the annotations: credit cost (1 credit each), caching behavior, and the explicit disclaimer that it does no SMTP probing and sends nothing. The annotations (readOnlyHint=false, openWorldHint=true) signal side effects, and the credit/caching disclosure complements them well.

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?

Front-loads the core purpose, then the conditional provider behavior, then return values, then a negative boundary. Four dense sentences, each carrying information with no padding.

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 no output schema, the description still documents the return shape (status enum values, confidence, individual checks) and the cost/behavior of each path, so an agent has everything needed to call it 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%, so the baseline is 3, but the description enriches use_provider beyond the schema's terse 'Also run the Hunter verifier' by tying it to a Hunter key requirement, the credit cost, and caching.

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?

Clear specific verb+resource: 'Check whether email addresses are deliverable,' and it enumerates the actual checks performed (syntax, MX, disposable domain, role address). This is distinct from the search/enrich siblings, though it never names an alternative explicitly to lock in the differentiation.

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 a concrete condition for the optional path ('With use_provider=true and a Hunter key...') and states the local checks always run, plus a negative boundary ('Does not do SMTP probing or send anything'). It stops short of explicitly routing the agent against any sibling tool.

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