Check if a phone number is registered on WhatsApp
AI agents call check_number to retrieve information from Mcp Ap2 without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool performs a lookup query to determine WhatsApp registration status of a phone number. It retrieves data with no side effects, no state changes, no code execution, and no financial impact. While it may have privacy implications, the security category is 'Read' as defined by the MCP classification scheme.
From the tool's definition Tool name 'check_number' and description 'Check if a phone number is registered on WhatsApp' indicate a query operation that retrieves information without modification, deletion, or execution of code.
Documented attack patterns abuse exactly the kind of access check_number gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Mcp Ap2, and nothing reaches the server without passing your rules. This is the rule we recommend for check_number:
{
"version": "1",
"default": "deny",
"tools": {
"check_number": {}
}
}check_number is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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Check if a phone number is registered on WhatsApp. It is categorised as a Read tool in the Mcp Ap2 MCP Server, which means it retrieves data without modifying state.
Register the Mcp Ap2 MCP server in PolicyLayer and add a rule for check_number: 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 Mcp Ap2. Nothing to install.
check_number 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 check_number 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 check_number. 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.
check_number is provided by the Mcp Ap2 MCP server (@codespar/mcp-ap2). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Mcp Ap2, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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1300 Mcp Ap2 tools catalogued and risk-classified — across an index of 43,000+ MCP servers.