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

Adds substantial context beyond the readOnlyHint/openWorldHint annotations: per-record partial failure ('one bad record fails only itself'), the auth requirement via 'key', the submission-order/index guarantee, the absence of suggestions, and the truncated field set (risk, complainer, reason absent). These are exactly the traits an agent cannot infer from the annotations.

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 capability and packs important behavioral facts into a compact block, but the opening two clauses are redundant ('Verify up to 100 email addresses in one call. Up to 100 records per call'). Otherwise every sentence carries useful 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?

With no output schema, the description compensates by naming the returned recommendation and disposable flag and listing the omitted fields, plus failure and auth semantics. An agent has everything needed to call it correctly and interpret partial results.

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 all three parameters (key, emails, policy) are already documented, and the ordering/index language for 'emails' plus the key requirement largely duplicate the schema's own descriptions. The 'policy' parameter is never addressed in the description, so no meaningful semantics are added beyond the structured fields; baseline 3 applies.

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 (verify), resource (email addresses) and scope (up to 100 in one call), which cleanly separates it from the singular verify_email and the other verify_*_batch siblings. An agent knows exactly what operation it is choosing without opening a 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 clear context for batch use and compares against single verification ('batch returns less detail than single verification'), which implies the batch/single tradeoff. It never states an explicit cut-off or 'use verify_email instead when...' rule, so the routing guidance is inferential rather than prescriptive.

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