wa_check_number_exists
Check if a phone number is registered on WhatsApp. Returns the JID if the number exists.
This record as markdown: /tools/delltrak-wamcp/wa-check-number-exists.md
What wa_check_number_exists does on WA MCP
AI agents call wa_check_number_exists to retrieve information from WA MCP without modifying anything. It is typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
Why wa_check_number_exists is rated Low
This tool performs a lookup to determine whether a phone number has a WhatsApp account and returns metadata (JID). It is a non-destructive information retrieval operation with no side effects on data or system state. While it could be used for reconnaissance (discovering valid accounts), the direct blast radius is limited to information exposure rather than account compromise, unauthorized messaging, or deletion.
From the tool's definition Tool name 'wa_check_number_exists' and description 'Check if a phone number is registered on WhatsApp. Returns the JID if the number exists.' indicate a query operation that retrieves information without modifying, deleting, or executing external actions.
Attacks that exploit this kind of access
The rule that runs wa_check_number_exists safely
PolicyLayer is an MCP gateway: it sits between your AI agents and WA MCP, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For wa_check_number_exists, this is the rule to start with:
wa_check_number_exists is read-only, so it stays allowed. Everything else on the server is denied unless you say otherwise.
The button opens the PolicyLayer dashboard: create your workspace, connect WA MCP, apply this rule, and every wa_check_number_exists call is checked against it from then on.
Questions about wa_check_number_exists
Check if a phone number is registered on WhatsApp. Returns the JID if the number exists. It is categorised as a Read tool in the WA MCP MCP Server, which means it retrieves data without modifying state.
Register the WA MCP server in PolicyLayer and add a rule for wa_check_number_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 WA MCP. Nothing to install.
wa_check_number_exists 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 wa_check_number_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.
Set action: deny in the PolicyLayer policy for wa_check_number_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.
wa_check_number_exists is provided by the WA MCP server (delltrak/wamcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
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