Configure pay-as-you-go billing for a client
AI agents use set_client_payg_billing to commit financial operations through Campaign Monitor MCP — usually the final step of a payment, billing, or trading workflow. A call moves real money.
This tool modifies financial billing settings for a client account. Pay-as-you-go billing determines how charges are incurred and applied, making this a financial operation. Misconfiguration could result in unexpected charges or financial commitments. Severity is critical due to potential for significant unintended financial impact.
From the tool's definition 'Configure pay-as-you-go billing for a client' — directly sets up billing configuration which commits financial obligations on a per-use basis
Attacks that exploit this kind of access
Configure pay-as-you-go billing for a client. It is categorised as a Financial tool in the Campaign Monitor MCP MCP Server, which means it involves financial transactions. Block by default and require explicit approval.
Register the Campaign Monitor MCP server in PolicyLayer and add a rule for set_client_payg_billing: 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 Campaign Monitor MCP. Nothing to install.
set_client_payg_billing is a Financial tool with critical risk. Critical-risk tools should be blocked by default and only enabled with explicit human approval.
Yes. Add a rate_limit block to the set_client_payg_billing 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 set_client_payg_billing. 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.
set_client_payg_billing is provided by the Campaign Monitor MCP server (pauliowest/cmon-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
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