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

readOnlyHint=true already tells the agent this is a safe read, and the description adds the useful detail that the response carries names, birth dates, and contact methods. It does not disclose pagination, ordering, or behavior for contacts with no individuals, so it adds only modest value beyond the annotation.

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?

A single dense sentence front-loads the purpose and returned fields, followed by a short endpoint reference. Nothing is wasteful, though the API endpoint adds little for an agent that cannot call it directly.

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 one required param, no nested objects, and no output schema, the description is nearly sufficient: it enumerates the return payload fields, which compensates for the missing output schema, and is consistent with the read-only annotation. Only pagination/ordering behavior is left unexplained.

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% for the single contact_id parameter, so the schema already carries the semantics. The description reinforces that the id refers to a contact/household but adds no format or constraint detail beyond what the schema provides; 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 (list) and resource (individuals belonging to a contact/household), and enumerates the returned fields (names, birth dates, emails, phones). This clearly distinguishes it from get_contact or list_contact_notes/gifts/tags siblings.

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?

Usage is implied by the 'belong to a contact/household' scoping, but there is no explicit when-to-use guidance, no statement of when not to use it, and no pointer to alternatives such as get_contact (which may also surface individuals).

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