AI agents use send_message to create or update resources in WhatsApp Web MCP — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your WhatsApp Web MCP environment.
This tool creates new data (messages) and modifies the communication state reversibly. While messages can be deleted, the primary action is creation/transmission. Severity is high because an AI agent sending unsolicited or misleading messages at scale could damage user relationships, enable fraud, or facilitate harassment.
From the tool's definition Tool name 'send_message' combined with server context indicating 'automated messaging' and 'AI-driven workflows' demonstrates this creates new message data in WhatsApp.
Documented attack patterns abuse exactly the kind of access send_message gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and WhatsApp Web MCP, and nothing reaches the server without passing your rules. This is the rule we recommend for send_message:
{
"version": "1",
"default": "deny",
"tools": {
"send_message": {
"limits": [
{
"counter": "send_message_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}send_message stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.
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send_message. It is categorised as a Write tool in the WhatsApp Web MCP MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the WhatsApp Web MCP server in PolicyLayer and add a rule for send_message: 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 WhatsApp Web MCP. Nothing to install.
send_message is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the send_message 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 send_message. 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.
send_message is provided by the WhatsApp Web MCP server (pnizer/wweb-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 13 WhatsApp Web MCP tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
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13 WhatsApp Web MCP tools catalogued and risk-classified — across an index of 42,500+ MCP servers.