> ## Documentation Index
> Fetch the complete documentation index at: https://developers.staging01.melio.com/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# API Simulator

> A hands-on UI to explore the Melio API - create businesses, add accounts, and submit payments, and watch every request and response live.

The API Simulator is a hands-on interface for exploring the Melio API without writing a single line of code. Create a business, add accounts, submit a payment, and watch the exact API requests and responses as you go. It's the fastest way to understand the power of the Melio API and see how the pieces fit together.

<Note>
  The Simulator requires your **partner API key**. Paste the key you received when your partner account was created - it's held in memory for the session only and is never stored or sent anywhere but the Melio API.
</Note>

## Connect your key

Open the Simulator and paste your staging partner API key, then choose **Connect & open simulator**. The key authenticates every call the Simulator makes on your behalf.

<Frame>
  <img src="https://mintcdn.com/melio/bGkEa16iDUGeXY1L/images/simulator-connect-1.png?fit=max&auto=format&n=bGkEa16iDUGeXY1L&q=85&s=59367e4f0949959868e2575b812ff1a5" alt="Simulator Connect 1" width="958" height="952" data-path="images/simulator-connect-1.png" />
</Frame>

## What you can do

The Simulator gives you the entire flow through a full UI:

* **Create a business** - onboard a payer as a legal entity (name, business type, tax info, address, and contact).
* **Add internal accounts** - the sources money is pulled from, via raw ACH (account and routing number), Plaid, or a tokenized card.
* **Add external accounts** - the delivery methods that define how vendors get paid.
* **Submit payments** - create a payment and follow it through its lifecycle.
* **Webhooks** - review the events your integration would receive.

<Frame>
  <img src="https://mintcdn.com/melio/bGkEa16iDUGeXY1L/images/simulator-overview.png?fit=max&auto=format&n=bGkEa16iDUGeXY1L&q=85&s=08b2dd951309c3985a6075676c97043a" alt="Simulator Overview" width="3832" height="1180" data-path="images/simulator-overview.png" />
</Frame>

## See every request and response

Alongside the UI, a live **request log** shows every API call the Simulator makes - the method, path, and status code. Expand any entry to see the full request and the JSON response Melio returned.

This makes the Simulator a great way to learn the shape of the API: take an action in the UI, then read exactly which endpoints were called and what came back.

```json theme={null}
GET /entities/ent_9b182c5e-3b3d-4bd8-a2bd-32db92e401ba  →  200

{
  "id": "ent_9b182c5e-3b3d-4bd8-a2bd-32db92e401ba",
  "type": "business",
  "externalId": "partner-biz-wrx510",
  "name": "Erez API Test",
  "legalName": "Acme Supplies LLC",
  "businessType": "corporation",
  "taxInfo": { "type": "ein", "identifierLast4": "6789" },
  "address": { "line1": "350 5th Ave", "city": "New York", "state": "NY", "postalCode": "10118", "countryCode": "US" },
  "industry": { "naicsCode": "424410", "name": "General Line Grocery Merchant Wholesalers" }
}
```

## Create real payments in staging

Everything in the Simulator runs against the **staging** environment, so you can create payments end to end without moving real money. It's a safe place to try flows, trigger risk controls, and confirm your understanding before you build.

<Note>
  Payments created in the Simulator are test payments on staging - no real funds move.
</Note>

<CardGroup cols={2}>
  <Card title="Getting Started" icon="rocket" href="/docs/reference/getting-started">
    Apply for beta access and get the API key you'll use here.
  </Card>

  <Card title="API Reference" icon="code" href="/docs/api-reference">
    The full endpoint reference behind everything the Simulator does.
  </Card>
</CardGroup>