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

Beyond the readOnly/idempotent/openWorld annotations, it discloses the guessing strategy, that the first confirmed pattern is returned with a confidence value, the catch-all-domain edge case where confirmation is impossible, and the billing model ($0.10 per successful call, failures free). That is exactly the operational detail an agent cannot get from structured fields.

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 action, then the algorithm, the edge case, the use case, and finally pricing — a sensible ordering with no filler. It is a touch long, and the "first.last, flast, first, and so on" enumeration is illustrative rather than load-bearing.

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 an output schema present, return values needn't be explained, and the annotations cover the safety profile; the description fills in algorithm, confidence, catch-all behavior and cost. The only unaddressed element is the optional api_key parameter's role in this specific tool, which the schema already documents.

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% with per-parameter descriptions for first_name, last_name, domain and api_key, so the schema carries the burden. The description only restates that inputs are a name and a company website and adds nothing about formats, length limits, or the api_key/payment behavior. 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 (find a person's work email) plus the inputs it derives from (name and company website), which cleanly separates it from the sibling email_verify that checks an address already in hand. An agent can pick this tool 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?

"Use it to reach a specific person at a company" gives a clear usage context, and the description implies the agent should have a name and domain rather than an existing address. It never names the obvious alternative (email_verify) or states when not to use it, so it stops short of explicit routing.

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