waha_check_contact_exists

THE RISK

Low Risk

Why waha_check_contact_exists needs a policy

This tool performs a lookup/query operation to verify whether a given phone number has an active WhatsApp account. It only retrieves status information and does not create, modify, delete, or execute any actions.

From the tool's definition Tool name 'waha_check_contact_exists' and description 'Check if phone number is registered on WhatsApp' indicate a query operation that retrieves information about contact existence with no side effects or modifications.

Documented attack patterns abuse exactly the kind of access waha_check_contact_exists gives an agent:

POLICY

How to control waha_check_contact_exists

PolicyLayer is an MCP gateway — it sits between your AI agents and WAHA MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for waha_check_contact_exists:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "waha_check_contact_exists": {}
  }
}

waha_check_contact_exists is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.

Create a free account and register WAHA MCP Server — nothing to install.
Add this policy — paste it, or build it visually.
Point your MCP client (Claude, Cursor, anything) at your gateway URL.

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EXPLORE

Related tools and policies

More WAHA MCP Server tools

Destructive waha_clear_chat_messages Clear all messages from a chat. WARNING: This is a destructive operation that cannot be un Destructive waha_delete_chat Delete a chat completely. WARNING: This is a destructive operation that cannot be undone. Destructive waha_delete_group_picture Remove group profile picture. Destructive waha_delete_message Delete a specific message from a chat. This is a destructive operation and cannot be undon Destructive waha_remove_group_participants Remove member(s) from a group. Requires admin privileges. Destructive waha_leave_group Leave a group. Execute waha_revoke_group_invite_code Revoke current invite link and generate a new one. Requires admin privileges. Write waha_demote_group_admin Remove admin privileges from participant(s). Requires admin privileges.

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Go deeper

The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Data exfiltration → How read access becomes an exfiltration channel when chained with untrusted content.
MCP token cost → What connecting this server costs in context-window tokens on every request.
Rate Limiting MCP Tool Calls: A Practical Guide →
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FAQ

Questions about waha_check_contact_exists

What does the waha_check_contact_exists tool do? +

Check if phone number is registered on WhatsApp. It is categorised as a Read tool in the WAHA MCP Server MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on waha_check_contact_exists? +

Register the WAHA MCP Server MCP server in PolicyLayer and add a rule for waha_check_contact_exists: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches WAHA MCP Server. Nothing to install.

What risk level is waha_check_contact_exists? +

waha_check_contact_exists is a Read tool with low risk. Read-only tools are generally safe to allow by default.

Can I rate-limit waha_check_contact_exists? +

Yes. Add a rate_limit block to the waha_check_contact_exists rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.

How do I block waha_check_contact_exists completely? +

Set action: deny in the PolicyLayer policy for waha_check_contact_exists. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.

What MCP server provides waha_check_contact_exists? +

waha_check_contact_exists is provided by the WAHA MCP Server MCP server (seejux/waha-whatsapp-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every WAHA MCP Server tool call.

Start from WAHA MCP Server, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.

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