Cancel a pending BTC transaction via RBF (sends funds back to self).
AI agents use tx_cancel to commit financial operations through Bitcoin wallet MCP server — usually the final step of a payment, billing, or trading workflow. A call moves real money.
This tool broadcasts a replacement Bitcoin transaction using Replace-By-Fee (RBF) to cancel a pending transaction. It moves funds on the Bitcoin network — even though the destination is 'self', it still commits a financial operation by broadcasting a new transaction with higher fees, consuming those fees irreversibly.
From the tool's definition Cancel a pending BTC transaction via RBF (sends funds back to self)
Attacks that exploit this kind of access
Cancel a pending BTC transaction via RBF (sends funds back to self). It is categorised as a Financial tool in the Bitcoin wallet MCP server MCP Server, which means it involves financial transactions. Block by default and require explicit approval.
Register the Bitcoin wallet MCP server MCP server in PolicyLayer and add a rule for tx_cancel: 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 Bitcoin wallet MCP server. Nothing to install.
tx_cancel 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 tx_cancel 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 tx_cancel. 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.
tx_cancel is provided by the Bitcoin wallet MCP server MCP server (markmhendrickson/mcp-server-bitcoin). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
tx_cancel is one line of Bitcoin wallet MCP server's registry record.
The record carries the whole server: verified identity, auth posture, risk grade, every tool classified, recommended policy — re-checked continuously.
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