Retrieve the contacts saved on a connected WhatsApp number and return their count.
List the contacts saved on the connected number. Read-only. To check whether a phone number has WhatsApp, use whatsapp_check_user. Returns the contacts and their count.
| Name | Required | Description | Default |
|---|---|---|---|
No arguments | |||
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=true and openWorldHint=true, so 'Read-only' adds little. However, the description adds return-shape information ('Returns the contacts and their count') that is not available anywhere else, since there is no output schema. It still omits any pagination or volume behavior for potentially large contact lists.
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 short sentences, front-loaded with what is listed and scoped before the routing hint and the return note. Every sentence earns its place apart from the slightly redundant 'Read-only'.
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 parameterless list tool, the description covers purpose, the relevant alternative, and the return shape, which is all an agent needs given the read-only annotations. No output schema means the return note is the right level of detail.
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?
The tool takes zero parameters, so the baseline is 4; there is no parameter surface the description needs to compensate for. Nothing in the description misrepresents inputs.
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 the contacts saved on the connected number') and scopes it to the connected account, which separates it from account-agnostic siblings. It also explicitly names a sibling it is not (whatsapp_check_user), so an agent can route without opening schemas.
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?
Provides an explicit alternative with the condition that selects it: 'To check whether a phone number has WhatsApp, use whatsapp_check_user.' It does not address when to prefer this over whatsapp_get_contact (single) or whatsapp_sync_contacts, so it stops short of full when/when-not coverage.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.