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

The description adds meaningful behavioral context beyond annotations: it is asynchronous ('Returns immediately with a job'), and it discloses a side effect that matters to downstream systems ('Lead rows get their email_status updated in place, which is what campaign lead filters read'). This is exactly the kind of non-obvious behavior an agent needs to know.

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?

Three short sentences, no filler, and the most decision-relevant facts are front-loaded: the action, the async return, and the poll target. The side-effect warning earns its place.

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?

Given there is no output schema, the description adequately explains the non-obvious return behavior (a job to poll) and the mutation side effect. It could go slightly further by specifying what the returned job looks like, but the pointer to verify_list_status covers the workflow.

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%, with list_id and mode already described adequately. The description adds no extra parameter-level semantics beyond tying the operation to 'every address in a list'. Baseline 3 is appropriate because the schema does the heavy lifting.

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 names a specific verb ('Start'), a clear resource ('bulk verification for every address in a list'), and an immediate outcome ('Returns immediately with a job'). It also differentiates itself from the sibling verify_list_status by positioning this as the starter and that one as the poller.

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 clearly frames when to use it: when you want to start bulk verification for an entire list. It also gives the follow-up step ('poll verify_list_status'), which is useful workflow guidance. It does not explicitly exclude single-address alternatives like verify_email, but the scope is clear enough.

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