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

Annotations cover the safety profile (openWorldHint=true, idempotentHint=true, destructiveHint=false), and the description adds two pieces of context the annotations don't: the per-call cost ('1 credit') and the best-effort caveat that mailbox verification only happens 'when the server allows'. It still doesn't explain latency, failure modes, or why readOnlyHint is false for what reads like a lookup.

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 sentences, front-loaded with the verb and resource, then a compact enumeration of outputs plus the credit cost. The output list is long but each item carries information; nothing is 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 no output schema, the description carries the return-value burden and does so by listing every signal returned, including the accept/review/reject recommendation. It is only incomplete on the undocumented bypass_cache parameter and on error/timeout behavior.

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 0% for two parameters. 'address' is self-evident from its name, but 'bypass_cache' is never mentioned anywhere, so the description leaves half the parameter surface unexplained when it is the only source that could compensate.

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 states a specific verb (check/verify) and resource (email address) and enumerates exactly what is examined: syntax, mail server, mailbox, disposable, role account, typo suggestion, risk score, and a recommendation. That enumeration cleanly separates it from siblings such as reverse_email (which goes the other direction) and validate_phone/verify_contact.

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?

There is no when-to-use or when-not-to-use guidance, and no sibling is named as an alternative. An agent must infer that this is the tool for validating an address it already holds, which is implied but never stated.

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