contacts

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

With no annotations, the description carries the full burden; it does disclose that this is a read operation and that list uses offset pagination via limit/skip, which is genuine behavioral context. It does not cover permissions/authorization nuances (e.g., whether common_groups works for contacts not in the address book), rate limits, or what the response contains and whether more pages exist.

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 stated in the first line, followed by a scannable action list and two short examples; each line earns its place. The two example lines are marginally redundant with the action bullets but still aid selection.

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?

For a 5-parameter, action-dispatch tool with no annotations and no output schema, the description covers inputs and actions but says nothing about return values or how paginated results signal completion. The per-action coupling of parameters (e.g., chat_id only for common_groups) is implied by the bullets but not stated explicitly.

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 0%, so the description must define the parameters, and it largely does: query is the filter for list, limit/skip implement offset pagination, and chat_id is the contact JID with a concrete example format (12345@c.us). The action enum is explained action-by-action; only the limit ceiling (200) is left to the schema.

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 opens with a specific verb+resource ("Read WhatsApp contacts known to the connected engine") and enumerates the two supported actions (list, common_groups) with their semantics. It never names a sibling (chats, groups) as the alternative for contact-adjacent needs, so differentiation from siblings is only implicit.

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 per-action examples ("find contacts named Douglas", "what groups do I share with...") show how each action is intended to be used, which is real guidance for picking the right action. However, there is no explicit when-not guidance or routing to sibling tools such as groups or chats, so an agent must infer the boundary.

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