The docs, but human first.

import { createWalletClient, http, parseUnits } from 'viem';
import { mainnet } from 'viem/chains';
import { privateKeyToAccount } from 'viem/accounts';

// Your signer. The MCP never sees this.
const account = privateKeyToAccount(process.env.SIGNER_KEY as `0x${string}`);
const wallet = createWalletClient({ account, chain: mainnet, transport: http() });

// Ask stake.link's MCP to build the unsigned stake call.
const res = await fetch('https://www.stakedotlink.money/mcp', {
  method: 'POST',
  headers: { 'Content-Type': 'application/json' },
  body: JSON.stringify({
    jsonrpc: '2.0',
    id: 1,
    method: 'tools/call',
    params: {
      name: 'sdl_build_stake_link',
      arguments: {
        amount_link: parseUnits('10', 18).toString(),
        from: account.address,
      },
    },
  }),
}).then((r) => r.json());

// Tool output is a JSON string inside the first content block.
const tx = JSON.parse(res.result.content[0].text) as {
  to: `0x${string}`;
  data: `0x${string}`;
  value: string;
  chainId: 1;
  approval?: { to: `0x${string}`; data: `0x${string}`; value: string };
  metadata: { action: string; inputAmount: string; notes?: string[] };
};

// If the builder returned an approval, sign it first.
if (tx.approval) {
  await wallet.sendTransaction({
    to: tx.approval.to,
    data: tx.approval.data,
    value: BigInt(tx.approval.value),
  });
}

// Sign the main call. LINK uses ERC677 transferAndCall, so no approval here.
const hash = await wallet.sendTransaction({
  to: tx.to,
  data: tx.data,
  value: BigInt(tx.value),
});

console.log(tx.metadata.action, hash);