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

No annotations are provided, so the description carries the full disclosure burden. It covers caching behavior, cost, the payment_required path, retry after checkout, and the unknown result semantics, and cautions the agent not to fabricate results. This is rich non-obvious behavioral information beyond the schema.

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?

The description is dense and front-loaded, with each sentence carrying useful information: action, cost/caching, payment recovery, and result semantics. No filler or repetition of schema fields.

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 no output schema and no annotations, the description covers the main non-obvious scenarios (cached, paid, unpaid, incomplete) well enough to guide invocation and follow-up. It does not enumerate every success result value, but it provides the critical unknown and payment_required cases and warns against inventing 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 the schema already describes both parameters. The description adds meaningful behavior for workspace_token by telling the agent to persist it as Authorization: Bearer and retry after payment, which is not present in the schema.

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?

Description explicitly states the core action 'Verify one email now' with a clear verb and resource. It also distinguishes itself from listing operations with '(listing tools is not a verify)', helping an agent avoid category confusion.

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 gives concrete usage context: cached repeats are free, fresh checks cost 1, and it explains the payment flow with checkout_url and token persistence. It does not name sibling tools like balance or buy_credits as alternatives, but it clearly indicates this is the tool for a single verification and excludes listing-type operations.

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