Finalize a fully-signed multi-sig PSBT (typically the output of combine_btc_psbts once the threshold is met) and extract the broadcast-ready tx hex. Refuses with a per-input breakdown when any input is below its threshold (e.g. "input 0: 1/2 signatures"). Pass broadcast: true to send via the conf...
AI agents use finalize_btc_psbt to commit financial operations through VaultPilot MCP — usually the final step of a payment, billing, or trading workflow. A call moves real money.
| Parameter | Type | Required | Description |
|---|---|---|---|
broadcast | boolean | — | When true, broadcasts the finalized tx via the configured indexer and returns `broadcastedTxid` alongside `txid`. When false (default), only returns the tx hex |
psbtBase64 | string | Yes | Base64-encoded PSBT v0 with all required signatures spliced in (typically via `combine_btc_psbts`). Refused with a per-input breakdown when any input is below i |
Parameters from the server's own tool schema.
finalize_btc_psbt moves real money, and an autonomous agent will call it with the same confidence it calls a search tool. A misread instruction or an injected prompt is all it takes to drain an account or blow a budget.
Attacks that exploit this kind of access
Finalize a fully-signed multi-sig PSBT (typically the output of combine_btc_psbts once the threshold is met) and extract the broadcast-ready tx hex. Refuses with a per-input breakdown when any input is below its threshold (e.g. "input 0: 1/2 signatures"). Pass broadcast: true to send via the configured indexer in the same call — returns broadcastedTxid on success. Pass broadcast: false (default) when the caller wants to inspect the hex first or broadcast through a different relay. No device touch. It is categorised as a Financial tool in the VaultPilot MCP MCP Server, which means it involves financial transactions. Block by default and require explicit approval.
finalize_btc_psbt accepts 2 parameters: broadcast, psbtBase64. Required: psbtBase64. The full parameter table on this page comes from the server's own tool schema.
Register the VaultPilot MCP server in PolicyLayer and add a rule for finalize_btc_psbt: 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 VaultPilot MCP. Nothing to install.
finalize_btc_psbt 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 finalize_btc_psbt 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 finalize_btc_psbt. 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.
finalize_btc_psbt is provided by the VaultPilot MCP server (vaultpilot-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.