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

The description adds important behavioral details beyond the annotations: the credit is charged only when a person is found with email or phone, saveToContacts has a storage side effect, and sending an Idempotency-Key makes retries safe. This gives the agent an accurate cost and safety profile.

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?

Four short sentences deliver the purpose, lookup modes, return content, billing behavior, side effect, and retry guidance without any redundant phrasing. The most important operational constraint, the credit charge, is front-loaded after the purpose statement.

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?

The description is complete for a single-person lookup tool: it covers accepted inputs, output highlights, billing, side effects, and retry safety. Because an output schema exists, the return details do not need to be spelled out. The only implicit requirement, that at least one identifier must be supplied, is strongly implied by 'by LinkedIn URL, email, or name and company domain.'

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 documents all parameters. The description adds meaning beyond the schema by clarifying that saveToContacts stores the person in contacts and by tying the charge to a successful person-with-contact-info result, which helps the agent reason about cost and side effects for each parameter.

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 description states a specific verb ('Look up'), a single resource ('one person'), and the three accepted identifier modes ('LinkedIn URL, email, or name and company domain'). This clearly differentiates it from the sibling search tools, which imply multiple results, and from persons_find_email/persons_find_phone, which target a single contact channel.

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 clear usage context: use this tool when you need one person and have a known identifier such as LinkedIn URL, email, or name plus company domain. It does not explicitly name alternatives or exclusion conditions such as 'use persons_search for broad lookups,' so it falls just short of a 5.

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