The connection between your broker and an AI signal system is the key to automated trading. This guide shows you step by step how to set up the API connection — using Interactive Brokers and CapTrader as examples.

What Is a Trading API?

An API (Application Programming Interface) is an interface through which two software systems communicate. In the trading context, this means: Your AI system sends buy and sell orders directly to your broker, without you having to click manually.

Prerequisites

An active broker account with live trading authorization
API access enabled (some brokers require separate application)
Stable internet connection
Basic understanding of order types (Market, Limit, Stop)

Step 1: Generate API Key

At Interactive Brokers:

Log into the Client Portal
Go to Settings, then API, then API Settings
Enable the ActiveX/Socket Client
Set a Master API Client ID
Note the IP address you will connect from

At CapTrader, the process is identical since CapTrader runs on IB infrastructure.

Step 2: Security Settings

API access is a security risk if misconfigured. Essential precautions:

IP whitelist: Only allow known IP addresses
Read-only vs. trading: Start with read-only access for testing, enable trading only when everything works
Maximum order size: Set a limit to prevent a bug from accidentally putting your entire account into one trade
Daily loss limit: Automatic stop when daily losses exceed a threshold

Step 3: Connection in Dieter Dashboard

At the Dieter Investment Club, the connection is intentionally simple:

Open Dashboard, then Settings, then Broker Connection
Select broker (Interactive Brokers / CapTrader)
Enter API key and port
Test connection — the system sends a test request
Activate paper trading mode for the first week

Step 4: First Test Orders

Before real money flows, test the connection thoroughly:

Paper trade: Buy 1 share of a blue-chip stock
Check: Was the order transmitted correctly?
Check: Are price, quantity, and order type correct?
Check: Is the position displayed correctly in the dashboard?

Common Errors and Solutions

Connection drops: Usually a firewall issue. Ensure port 7496 (live) or 7497 (paper) is not blocked.

Orders rejected: Check trading permissions in the broker account. Some products (options, futures) must be separately enabled.

Wrong position sizes: Ensure the currency in the API system matches the account currency (EUR vs. USD).

Bottom Line: API setup is a one-time effort that pays off long-term. Take the time for a thorough setup — the first 30 minutes save you hours of manual clicking later.