Refund a transaction. POST /transactions/{transactionId}/refund. AMOUNT IN CENTS: e.g. 250 = $2.50, 5500 = $55.00. Required: transactionId, amount (integer cents).
AI agents use refund_transaction to commit financial operations through Rebillia MCP Server — usually the final step of a payment, billing, or trading workflow. A call moves real money.
This tool moves money by issuing refunds, which commits financial obligations and reverses prior payment transactions. Misuse by an AI agent could refund arbitrary amounts to arbitrary transactions, causing direct financial loss. This is the most severe category per the hierarchy.
From the tool's definition Tool name 'refund_transaction' combined with description stating it refunds transactions by posting to /transactions/{transactionId}/refund. Requires transactionId and amount in cents, directly manipulating financial transactions.
Attacks that exploit this kind of access
Refund a transaction. POST /transactions/{transactionId}/refund. AMOUNT IN CENTS: e.g. 250 = $2.50, 5500 = $55.00. Required: transactionId, amount (integer cents). It is categorised as a Financial tool in the Rebillia MCP Server MCP Server, which means it involves financial transactions. Block by default and require explicit approval.
Register the Rebillia MCP Server MCP server in PolicyLayer and add a rule for refund_transaction: 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 Rebillia MCP Server. Nothing to install.
refund_transaction 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 refund_transaction 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 refund_transaction. 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.
refund_transaction is provided by the Rebillia MCP Server MCP server (rhinosaas/rebillia-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Every MCP server has a record like this.
Type a name, get the same breakdown: verified identity, auth posture, risk grade, capabilities, recommended policy.
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