# prepare_btc_send

Build an unsigned Bitcoin native-send PSBT (segwit/taproot only in Phase 1). Returns a 15-min handle the agent forwards to send_transaction; the Ledger BTC app clear-signs every output (address + amount) + fee on-screen, so there is NO blind-sign hash to pre-match in chat. The verification block surfaces every output's address, amount in BTC, isChange flag, fee (BTC + sat/vB), and RBF flag. Fee selection: pass feeRateSatPerVb for an explicit sat/vB number, OR feePriority for a fuzzy preset (fastestFee / halfHourFee / hourFee / economyFee / minimumFee — issue #435) that resolves to mempool.space's named buckets at prepare time. Default (neither set) is halfHourFee. The resolved sat/vB always appears in the response under feeRateSatPerVb so the user sees what was picked. Coin-selection runs branch-and-bound + accumulative fallback via the coinselect library; a fee-cap guard refuses any tx whose fee exceeds max(10 × feeRate × vbytes, 2% of total output value) unless allowHighFee: true is passed. RBF is enabled by default (sequence 0xFFFFFFFD); pass rbf: false to mark final.

Agent View of the PolicyLayer registry record for `prepare_btc_send`. HTML page: https://policylayer.com/tools/io-github-szhygulin-vaultpilot-mcp/prepare-btc-send

## Facts

- Tool: `prepare_btc_send`
- Server: VaultPilot MCP (`vaultpilot-mcp`) — https://policylayer.com/tools/io-github-szhygulin-vaultpilot-mcp.md
- Install: `npx -y vaultpilot-mcp`
- Homepage: https://github.com/szhygulin/vaultpilot-mcp
- Risk category: Financial (Critical risk)
- Registry record: grade F, identity unverified
- Server rate-limited: no
- Parameters: 7 (3 required)
- Recommended policy verdict: Approval-gated

## Parameters

| Parameter | Type | Required | Description |
| --- | --- | --- | --- |
| `to` | string | yes | Bitcoin recipient address. Any of the four mainnet types is accepted as a destination — the restriction is only on the source side. |
| `rbf` | boolean | no | BIP-125 Replace-By-Fee. Default true → sequence 0xFFFFFFFD on every input, marking the tx replaceable so the user can fee-bump if it stalls. Set false → 0xFFFFF |
| `amount` | string | yes | Decimal BTC string (up to 8 fractional digits, e.g. "0.001") or "max" to sweep the full balance minus fees. "max" picks the fee-aware amount after coin-selectio |
| `wallet` | object | yes | One paired Bitcoin source address (string), OR an array of 1-20 paired source addresses for multi-input consolidation (issue #264). All addresses must belong to |
| `feePriority` | string | no | Issue #435 — fuzzy-fee preset that resolves to mempool.space's named buckets (`fastestFee` ~next-block, `halfHourFee` ~3-block, `hourFee` ~6-block, `economyFee` |
| `allowHighFee` | boolean | no | Override the fee-cap guard. The cap is `max(10 × feeRate × vbytes, 2% of total output value)`. Legitimate priority sends through heavy congestion can exceed it; |
| `feeRateSatPerVb` | number | no | Fee rate in sat/vB. Optional — when omitted, uses mempool.space's `halfHourFee` recommendation (~3-block confirm target). Override for priority sends through co |

Parameters from the server's own tool schema.

## Example call (MCP tools/call, JSON-RPC 2.0)

```json
{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/call",
  "params": {
    "name": "prepare_btc_send",
    "arguments": {
      "to": "<to>",
      "amount": "<amount>",
      "wallet": {}
    }
  }
}
```

## Why prepare_btc_send is rated Critical

This tool constructs a Bitcoin payment transaction (PSBT) that is directly forwarded to send_transaction for execution. It moves cryptocurrency by preparing outputs with addresses and amounts. Even though it produces an unsigned PSBT, it is the first and essential step in a financial transfer pipeline, and misuse could result in funds being sent to wrong addresses.

From the tool's own definition: "Build an unsigned Bitcoin native-send PSBT... Returns a 15-min handle the agent forwards to send_transaction; the Ledger BTC app clear-signs every output (address + amount) + fee on-screen"

Risk signals: Bulk/mass operation — affects multiple targets

## Use case

AI agents use prepare_btc_send to commit financial operations through VaultPilot MCP, usually the final step of a payment, billing, or trading workflow. A call moves real money.

## Recommended policy (PolicyLayer)

Verdict: **Approval-gated**. Enforced by the PolicyLayer MCP gateway (https://policylayer.com/mcp-gateway) before a call reaches VaultPilot MCP:

```json
{
  "version": "1",
  "default": "deny",
  "tools": {
    "prepare_btc_send": {
      "deny_if": [
        {
          "conditions": [],
          "on_deny": "Requires human approval."
        }
      ]
    }
  }
}
```

## Other tools on VaultPilot MCP (188)

- `prepare_btc_lifi_swap` — Destructive — https://policylayer.com/tools/io-github-szhygulin-vaultpilot-mcp/prepare-btc-lifi-swap.md
- `prepare_btc_rbf_bump` — Destructive — https://policylayer.com/tools/io-github-szhygulin-vaultpilot-mcp/prepare-btc-rbf-bump.md
- `prepare_jito_stake` — Destructive — https://policylayer.com/tools/io-github-szhygulin-vaultpilot-mcp/prepare-jito-stake.md
- `prepare_marginfi_init` — Destructive — https://policylayer.com/tools/io-github-szhygulin-vaultpilot-mcp/prepare-marginfi-init.md
- `prepare_solana_nonce_close` — Destructive — https://policylayer.com/tools/io-github-szhygulin-vaultpilot-mcp/prepare-solana-nonce-close.md
- `prepare_sunswap_swap` — Destructive — https://policylayer.com/tools/io-github-szhygulin-vaultpilot-mcp/prepare-sunswap-swap.md
- `prepare_uniswap_v3_burn` — Destructive — https://policylayer.com/tools/io-github-szhygulin-vaultpilot-mcp/prepare-uniswap-v3-burn.md
- `prepare_uniswap_v3_mint` — Destructive — https://policylayer.com/tools/io-github-szhygulin-vaultpilot-mcp/prepare-uniswap-v3-mint.md
- `remove_contact` — Destructive — https://policylayer.com/tools/io-github-szhygulin-vaultpilot-mcp/remove-contact.md
- `unregister_btc_multisig_wallet` — Destructive — https://policylayer.com/tools/io-github-szhygulin-vaultpilot-mcp/unregister-btc-multisig-wallet.md
- `combine_btc_psbts` — Execute — https://policylayer.com/tools/io-github-szhygulin-vaultpilot-mcp/combine-btc-psbts.md
- `pair_ledger_btc` — Execute — https://policylayer.com/tools/io-github-szhygulin-vaultpilot-mcp/pair-ledger-btc.md
- `prepare_aave_repay` — Execute — https://policylayer.com/tools/io-github-szhygulin-vaultpilot-mcp/prepare-aave-repay.md
- `prepare_btc_multisig_send` — Execute — https://policylayer.com/tools/io-github-szhygulin-vaultpilot-mcp/prepare-btc-multisig-send.md
- `prepare_compound_repay` — Execute — https://policylayer.com/tools/io-github-szhygulin-vaultpilot-mcp/prepare-compound-repay.md
- `prepare_compound_supply` — Execute — https://policylayer.com/tools/io-github-szhygulin-vaultpilot-mcp/prepare-compound-supply.md
- `prepare_curve_swap` — Execute — https://policylayer.com/tools/io-github-szhygulin-vaultpilot-mcp/prepare-curve-swap.md
- `prepare_custom_call` — Execute — https://policylayer.com/tools/io-github-szhygulin-vaultpilot-mcp/prepare-custom-call.md
- `prepare_kamino_init_user` — Execute — https://policylayer.com/tools/io-github-szhygulin-vaultpilot-mcp/prepare-kamino-init-user.md
- `prepare_kamino_supply` — Execute — https://policylayer.com/tools/io-github-szhygulin-vaultpilot-mcp/prepare-kamino-supply.md
- `prepare_lido_unstake` — Execute — https://policylayer.com/tools/io-github-szhygulin-vaultpilot-mcp/prepare-lido-unstake.md
- `prepare_lido_unwrap` — Execute — https://policylayer.com/tools/io-github-szhygulin-vaultpilot-mcp/prepare-lido-unwrap.md
- `prepare_lido_wrap` — Execute — https://policylayer.com/tools/io-github-szhygulin-vaultpilot-mcp/prepare-lido-wrap.md
- `prepare_native_stake_deactivate` — Execute — https://policylayer.com/tools/io-github-szhygulin-vaultpilot-mcp/prepare-native-stake-deactivate.md
- `prepare_native_stake_delegate` — Execute — https://policylayer.com/tools/io-github-szhygulin-vaultpilot-mcp/prepare-native-stake-delegate.md
- `prepare_rocketpool_unstake` — Execute — https://policylayer.com/tools/io-github-szhygulin-vaultpilot-mcp/prepare-rocketpool-unstake.md
- `prepare_safe_tx_execute` — Execute — https://policylayer.com/tools/io-github-szhygulin-vaultpilot-mcp/prepare-safe-tx-execute.md
- `prepare_solana_lifi_swap` — Execute — https://policylayer.com/tools/io-github-szhygulin-vaultpilot-mcp/prepare-solana-lifi-swap.md
- `prepare_solana_nonce_init` — Execute — https://policylayer.com/tools/io-github-szhygulin-vaultpilot-mcp/prepare-solana-nonce-init.md
- `prepare_solana_swap` — Execute — https://policylayer.com/tools/io-github-szhygulin-vaultpilot-mcp/prepare-solana-swap.md
- …and 158 more: https://policylayer.com/tools/io-github-szhygulin-vaultpilot-mcp.md

## For agents

This record is a snapshot. Live verdicts and the full registry:

- Check every server in your MCP config at once: `npx -y policylayer stack`
- Vet a server before you add it: install the mcp-precheck skill — `npx skills add https://policylayer.com` (skill text: https://policylayer.com/skill.md)
- Query the registry over MCP: endpoint `https://api.policylayer.com/mcp` — tools `check_mcp_server`, `check_mcp_stack`, `check_tool`, `search_registry`, `get_change_events`

---

Source: the PolicyLayer MCP registry — one continuously verified record per MCP server. Full record: https://policylayer.com/registry?q=io-github-szhygulin-vaultpilot-mcp · API: https://policylayer.com/registry/api · Policy library: https://policylayer.com/policies/io-github-szhygulin-vaultpilot-mcp