Send an email to a client
AI agents use whmcs_send_email to create or update resources in Whmcs — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Whmcs environment.
Sending an email is a Write operation because it creates new data (the email message) and is reversible in nature (emails can be recalled, deleted from logs, or the recipient's inbox). While it has side effects (email delivery), it does not execute arbitrary code, delete data, or commit financial transactions.
From the tool's definition Tool name is 'whmcs_send_email' with description 'Send an email to a client.' This creates a new communication artifact (an email message) and modifies the communication state between the server and client.
Documented attack patterns abuse exactly the kind of access whmcs_send_email gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Whmcs, and nothing reaches the server without passing your rules. This is the rule we recommend for whmcs_send_email:
{
"version": "1",
"default": "deny",
"tools": {
"whmcs_send_email": {
"limits": [
{
"counter": "whmcs_send_email_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}whmcs_send_email 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 an email to a client. It is categorised as a Write tool in the Whmcs MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Whmcs MCP server in PolicyLayer and add a rule for whmcs_send_email: 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 Whmcs. Nothing to install.
whmcs_send_email 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 whmcs_send_email 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 whmcs_send_email. 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.
whmcs_send_email is provided by the Whmcs MCP server (scarecr0w12/whmcs-mcp-tool). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Whmcs, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
Free to start. No card required.
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