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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so the bar is lower, and the description still adds real behavior: ordering, pagination bounds, and the meaning of returned fields like is_test ('acts on nothing outward') and paused_at ('outreach paused'). That is substantive context beyond the 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?

Purpose is front-loaded in the first clause, then filtering, pagination, and return fields follow in a logical order with no filler. The pagination sentence duplicates the schema's default/max wording almost verbatim, a minor redundancy that keeps it from a 5.

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 correctly takes on the burden of describing returned rows (lead_status, utm_*, attributes, etc.), which is exactly what an agent needs. It stops short of telling the agent how to detect the end of pagination (no total count mentioned), a small gap for a list endpoint.

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 baseline is 3, but the description adds genuine meaning over the schema: it frames created_after/created_before as the way to answer 'leads in a period' and groups the params by task (filter / paginate). The limit/offset and include_deleted wording largely restates the schema, keeping this below a 5.

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 (list contacts) plus the default ordering (newest first), which immediately tells the agent what it gets back. It is clear but never differentiates itself from the prominent sibling search_contacts, so an agent still has to infer which one to pick.

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?

It offers usage context for the filters ('for leads in a period') and explains include_deleted, but that is parameter-level guidance rather than tool-selection guidance. It never states when to use this tool instead of search_contacts or get_contact, leaving the actual routing decision implicit.

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