Check if a phone number is registered on WhatsApp.
AI agents call whatsapp_check_user to retrieve information from WSAPI WhatsApp MCP Server without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool retrieves information about whether a phone number exists on WhatsApp. It performs no mutations, does not execute code, does not delete data, and does not involve financial transactions. The query-based nature with informational results only makes it a Read category tool.
From the tool's definition Tool name and description indicate it 'Check if a phone number is registered on WhatsApp' — a pure query operation with no data modification or side effects.
Attacks that exploit this kind of access
Check if a phone number is registered on WhatsApp. It is categorised as a Read tool in the WSAPI WhatsApp MCP Server MCP Server, which means it retrieves data without modifying state.
Register the WSAPI WhatsApp MCP Server MCP server in PolicyLayer and add a rule for whatsapp_check_user: 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 WSAPI WhatsApp MCP Server. Nothing to install.
whatsapp_check_user is a Read tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the whatsapp_check_user 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.
Set action: deny in the PolicyLayer policy for whatsapp_check_user. 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.
whatsapp_check_user is provided by the WSAPI WhatsApp MCP Server MCP server (wsapi-chat/wsapi-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Every MCP server has a record like this.
Type a name, get the same breakdown: verified identity, auth posture, risk grade, capabilities, recommended policy.
Teams ship this data inside their own products. See what a licence covers →