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

Beyond the annotations (readOnlyHint=false, idempotentHint=false, openWorldHint=true), the description discloses cost implications ('billable job and spend credits'), the guard parameter, the no-retry/no-poll contract, and the duplicate-job risk on timeout. These are the exact behaviors an agent needs to avoid charging credits twice.

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?

Every sentence carries distinct information: purpose, cost/confirmation, return value and next tool, retry behavior, and duplicate warning. The billable/confirm warning is front-loaded, which is where an agent needs it most.

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?

There is no output schema, but the description states the return shape ('a file ID'), names the consuming tool, and covers the side effects and failure modes of a non-idempotent, credit-spending call. Nothing essential for correct invocation is missing.

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%, so the description must compensate. It does clarify the operational meaning of `confirm` (a spend gate) and the 1–1,000 email range, but `filename` is never mentioned and no format expectations for `emails` are added beyond the schema's pattern.

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 first sentence states a specific verb and resource ('Create and upload a CSV of 1–1,000 emails for bulk verification'), which clearly separates it from the sibling single-address tool millionverifier_verify_email and the status tool millionverifier_file_info. An agent can identify the operation without opening the 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?

It gives explicit preconditions ('requires confirm:true'), routes the agent forward ('Returns a file ID for millionverifier_file_info'), and warns against a specific wrong action ('A timed-out submission may still create a job; check the dashboard before repeating it'). It also states that no automatic retry or polling occurs, removing ambiguity about follow-up behavior.

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