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What is the GOAT SDK plugin?

The @mandate.md/goat-plugin package wraps Mandate’s policy engine as a GOAT SDK plugin. It exposes two tools: mandate_transfer for ERC20 transfers and mandate_x402_pay for x402 payment flows. Every tool call validates against your Mandate spending policies before signing or broadcasting. The plugin extends PluginBase<EVMWalletClient> and works with any EVM chain supported by GOAT.

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Installation

bun add @mandate.md/goat-plugin @goat-sdk/core
@goat-sdk/core is a peer dependency (>=0.3.0). Install it alongside the plugin.

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Usage

import { mandate } from '@mandate.md/goat-plugin';
import { createWalletClient, http } from 'viem';
import { privateKeyToAccount } from 'viem/accounts';
import { baseSepolia } from 'viem/chains';

const walletClient = createWalletClient({
  account: privateKeyToAccount(process.env.PRIVATE_KEY as `0x${string}`),
  chain: baseSepolia,
  transport: http(),
});

const mandatePlugin = mandate({
  runtimeKey: process.env.MANDATE_RUNTIME_KEY!,
  privateKey: process.env.PRIVATE_KEY! as `0x${string}`,
  chainId: 84532,
  rpcUrl: 'https://sepolia.base.org',
});
Pass the plugin to your GOAT agent’s plugin list. The agent can now call mandate_transfer and mandate_x402_pay as tools.

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Tools

ToolDescription
mandate_transferTransfer ERC20 tokens with policy enforcement. Accepts to, amount, tokenAddress, and optional waitForConfirmation.
mandate_x402_payPay for an x402-gated resource. Accepts url and optional headers.
Both tools create a MandateWallet internally, validate the transaction against the Mandate API, sign locally, and broadcast. Your private key never leaves the process.

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Configuration

ParameterTypeRequiredDescription
runtimeKeystringYesMandate runtime key (mndt_live_... or mndt_test_...)
privateKey`0x${string}`YesAgent wallet private key (hex, with 0x prefix)
chainIdnumberNoEVM chain ID. Defaults to 84532 (Base Sepolia).
rpcUrlstringNoRPC endpoint URL. Defaults to the chain’s public RPC.

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Error handling

The plugin throws plain Error objects with descriptive messages. This matches GOAT SDK conventions where tool errors surface as strings to the LLM. 
// Policy block:
// "Transfer blocked by Mandate policy: daily_limit_exceeded"

// Approval required:
// "Transfer requires approval. IntentId: int_abc123"
If your agent needs structured error handling, use the @mandate.md/sdk directly. The SDK throws typed errors: PolicyBlockedError, ApprovalRequiredError, and CircuitBreakerError.
Store runtimeKey and privateKey in environment variables. Never hardcode credentials in source files.

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Next Steps

Integrations Overview

Compare all supported agent frameworks and choose the right one.

MandateWallet

Use MandateWallet directly for full control over the validate-sign-broadcast flow.

Handle Errors

Learn how to catch and respond to every Mandate error type.