Bitcoin SV MCP Server

import { type BroadcastFailure, type BroadcastResponse, P2PKH, PrivateKey, SatoshisPerKilobyte, Script, Transaction, Utils, fromUtxo, isBroadcastFailure, isBroadcastResponse, } from "@bsv/sdk"; import type { McpServer } from "@modelcontextprotocol/sdk/server/mcp.js"; import type { RequestHandlerExtra } from "@modelcontextprotocol/sdk/shared/protocol.js"; import type { CallToolResult, ServerNotification, ServerRequest, } from "@modelcontextprotocol/sdk/types.js"; import { BAP, MemberID } from "bsv-bap"; import { z } from "zod"; import { BsocialBroadcaster } from "../../utils/broadcaster"; import { friendPrivateKeyFromMemberIdKey, friendPublicKeyFromSeedString, } from "../../utils/keys"; import { MAP_PREFIX } from "../constants"; import { fetchPaymentUtxos, fetchPaymentUtxosFromV5, } from "../wallet/fetchPaymentUtxos"; import type { Wallet } from "../wallet/wallet"; const { toArray, toHex } = Utils; const APP_DOMAIN = "bsv-mcp"; export const bapFriendArgsSchema = z.object({ targetBapId: z.string().min(1, "targetBapId is required."), }); export type BapFriendArgs = z.infer<typeof bapFriendArgsSchema>; export interface BapFriendConfig { disableBroadcasting?: boolean; } export function registerBapFriendTool( server: McpServer, wallet: Wallet, xprv: string, config?: BapFriendConfig, ) { server.tool( "bap_friend", "Initiates a friend request to another BAP ID by broadcasting an on-chain MAP transaction.", { args: bapFriendArgsSchema }, async ( { args }: { args: BapFriendArgs }, extra: RequestHandlerExtra<ServerRequest, ServerNotification>, ): Promise<CallToolResult> => { const { targetBapId } = args; const logFunc = console.error; try { // --- Preconditions --- if (!xprv) { return { isError: true, content: [ { type: "text", text: "Server does not have a BAP master key (xprv). Cannot derive friend public key.", }, ], }; } const payPk = wallet.getPaymentKey(); const identityPk = wallet.getIdentityKey(); if (!identityPk || !payPk) { return { isError: true, content: [ { type: "text", text: !payPk ? "Wallet private key not available. Cannot fund friend request transaction." : "Wallet identity key not available. Cannot derive friend public key.", }, ], }; } // 3. Derive Initial Identity const bap = new BAP(xprv); const idpk = PrivateKey.fromWif( bap.newId().exportMemberBackup().derivedPrivateKey, ); const identityInstance = new MemberID(idpk); const paymentAddress = payPk.toAddress(); // --- Derive friend public key --- const friendPubKey = friendPrivateKeyFromMemberIdKey( identityPk, targetBapId, ) .toPublicKey() .toString(); // --- Build MAP payload --- const payloadParts: (string | number[])[] = [ MAP_PREFIX, "SET", "app", APP_DOMAIN, "type", "friend", "bapID", targetBapId, "publicKey", friendPubKey, ]; const payloadBuffers = payloadParts.map( (part) => toArray(part) as number[], ); const signedBuffers = identityInstance.signOpReturnWithAIP(payloadBuffers); const payloadHex = signedBuffers.map((b) => toHex(b)); const asmPayload = `OP_0 ${payloadHex.join(" ")}`; const opReturnScript = Script.fromASM(asmPayload); // --- Build Transaction --- const tx = new Transaction(); tx.addOutput({ lockingScript: opReturnScript, satoshis: 0 }); // --- Fund transaction --- const utxos = await fetchPaymentUtxosFromV5(paymentAddress); if (!utxos || utxos.length === 0) { return { isError: true, content: [ { type: "text", text: `No UTXOs available for payment address ${paymentAddress}. Cannot send friend request.`, }, ], }; } const feeModel = new SatoshisPerKilobyte(10); let totalInput = 0n; let estFee = await feeModel.computeFee(tx); for (const utxo of utxos) { if (totalInput >= BigInt(estFee)) break; const unlockTemplate = new P2PKH().unlock( payPk, "all", false, utxo.satoshis, Script.fromBinary(toArray(utxo.script, "hex")), ); const input = fromUtxo(utxo, unlockTemplate); tx.addInput(input); totalInput += BigInt(utxo.satoshis); estFee = await feeModel.computeFee(tx); } if (totalInput < BigInt(estFee)) { return { isError: true, content: [ { type: "text", text: `Not enough funds to cover fee. Needed ${estFee}, have ${totalInput}.`, }, ], }; } const change = totalInput - BigInt(estFee); if (change > 0n) { tx.addOutput({ lockingScript: new P2PKH().lock(paymentAddress), satoshis: Number(change), change: true, }); } await tx.fee(feeModel); await tx.sign(); const txHex = tx.toHex(); const txid = tx.id("hex"); if (config?.disableBroadcasting) { return { content: [ { type: "text", text: JSON.stringify({ success: true, disabledBroadcast: true, txid, rawTx: txHex, message: `Broadcasting disabled. Friend request transaction built for ${targetBapId}.`, }), }, ], }; } // --- Broadcast --- const broadcaster = new BsocialBroadcaster(); const broadcastResult = await tx.broadcast(broadcaster); let success = true; let errorMsg: string | undefined; let resultTxid = txid; if (isBroadcastResponse(broadcastResult as BroadcastResponse)) { resultTxid = (broadcastResult as BroadcastResponse).txid; } else if (isBroadcastFailure(broadcastResult as BroadcastFailure)) { success = false; const failure = broadcastResult as BroadcastFailure; errorMsg = `Broadcast failed: ${failure.description} (Code: ${failure.code})`; if (failure.txid) resultTxid = failure.txid; } return { isError: !success, content: [ { type: "text", text: JSON.stringify({ success, txid: resultTxid, rawTx: txHex, message: success ? `Friend request sent to ${targetBapId}.` : (errorMsg ?? "Broadcast failed"), }), }, ], }; } catch (err) { const errMsg = err instanceof Error ? err.message : String(err); return { isError: true, content: [ { type: "text", text: `Failed to send friend request: ${errMsg}`, }, ], }; } }, ); }