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

Annotations only flag non-read-only, non-idempotent, open-world; the description goes well beyond by disclosing that the call consumes a monthly quota with per-plan limits (Strategic 600, Pro 150), what happens on exhaustion (remaining count + upgrade path), live mailbox verification, and the possible result statuses. This is exactly the metered-operation context an agent needs before invoking.

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 dense sentences with zero filler, front-loaded with the cost implication before the usage trigger and the return/limit details. Every sentence carries information the agent needs.

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?

No output schema exists, and the description compensates by stating the return contents (status values and date). Combined with the quota behavior and usage routing, nothing material is missing for correct invocation.

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, including the cost warning on include_mobile. The description adds no syntax or format detail for 'company' beyond the schema, so the baseline of 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 ('spend one of the user's monthly contact reveals to find decision-maker emails at a company') and adds scope detail ('matched to the titles they sell to'). It is clearly distinguishable from the adjacent get_company_contacts sibling, which is named outright.

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?

Explicit trigger condition: 'Use this when get_company_contacts returns nobody, or nobody with an email.' It also names the alternative and warns that the call is metered, so the agent knows both when to prefer it and when not to.

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