const options = {
  method: 'POST',
  headers: {Authorization: 'Bearer <token>', 'Content-Type': 'application/json'},
  body: JSON.stringify({
    template_slug: '<string>',
    role: '<string>',
    party: {
      external_reference: '<string>',
      wallet_address: '<string>',
      name: '<string>',
      chain_id: 123
    },
    legs: [
      {
        instrument_id: '<string>',
        quantity: 1,
        direction: 'deliver',
        leg_type: 'asset_delivery',
        chain_id: 123,
        token_standard: '<string>'
      }
    ],
    timeout_at: '2023-11-07T05:31:56Z',
    idempotency_key: '<string>',
    trade_reference: '<string>',
    fee_mode: 'seller_pays',
    settlement_category: '<string>',
    maturity_at: '2023-11-07T05:31:56Z',
    repo_rate: 1,
    repayment_amount: 1
  })
};

fetch('https://api.keystoneos.xyz/v1/instructions', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

{
  "id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
  "trade_reference": "<string>",
  "status": "<string>",
  "settlement_id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
  "template_slug": "<string>",
  "role": "<string>",
  "party": {},
  "legs": [
    {}
  ],
  "timeout_at": "2023-11-07T05:31:56Z",
  "expires_at": "2023-11-07T05:31:56Z",
  "created_at": "2023-11-07T05:31:56Z"
}