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

No annotations are supplied, so the description carries the full behavioral burden. It does well on method ('Checks the domain's mail servers, reads the company's homepage and contact pages'), result ordering ('An exact address found on the site comes first'), and even the paid-access model ('Costs $0.005 USDC on Base via x402'), but it omits what happens when no candidates are found, error/refund behavior on a paid call, and any latency or rate-limit expectations.

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 tight sentences, front-loaded with the purpose, then mechanism, then output ordering, then cost. Every sentence carries distinct information and nothing is repeated from the schema or title.

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 does the necessary work of describing the return shape (ranked candidates, each with a confidence, exact-match first). For a paid, two-parameter lookup the remaining gap is edge-case behavior (empty result, failure handling), which is a modest omission rather than a blocking one.

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 100%, so both parameters are already documented with examples ('Jane Doe', 'stripe.com'). The description adds only that the domain drives pattern discovery and that patterns like jane.doe, jdoe, jane are considered, which is useful context but not parameter-level detail beyond the schema; 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 and resource ('Finds a person's likely work email') plus the exact inputs that produce it ('from their name and company domain'). This clearly separates it from the closest sibling, email_validate, which verifies an existing address rather than inferring one.

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 makes the use case clear and implicitly routes away from verification work by stating 'No SMTP probe', which tells the agent this produces guesses, not verified addresses. It stops short of an explicit 'use email_validate instead when you need confirmation' statement or any when-not-to-use exclusion.

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