Authentication

To access the Sim API, you need an API key. Sim supports two types of API keys — personal keys and workspace keys — each with different billing and access behaviors.

Key Types

Generating API Keys

To generate a personal key, open Account settings → Sim API keys. Workspace administrators can create shared keys from Workspace settings → Sim API keys.

Using API Keys

Pass your API key in the X-API-Key header with every request:

curl -X POST https://www.sim.ai/api/workflows/{workflowId}/execute \
  -H "Content-Type: application/json" \
  -H "X-API-Key: YOUR_API_KEY" \
  -d '{"inputs": {}}'

const response = await fetch(
  'https://www.sim.ai/api/workflows/{workflowId}/execute',
  {
    method: 'POST',
    headers: {
      'Content-Type': 'application/json',
      'X-API-Key': process.env.SIM_API_KEY!,
    },
    body: JSON.stringify({ inputs: {} }),
  }
)

import requests

response = requests.post(
    "https://www.sim.ai/api/workflows/{workflowId}/execute",
    headers={
        "Content-Type": "application/json",
        "X-API-Key": os.environ["SIM_API_KEY"],
    },
    json={"inputs": {}},
)

Where Keys Are Used

API keys authenticate access to:

• Workflow execution — run deployed workflows via the API
• Logs API — query workflow execution logs and metrics
• MCP servers — authenticate connections to deployed MCP servers
• SDKs — the Python and TypeScript SDKs use API keys for all operations

Security

• Keys use the sk-sim- prefix and are encrypted at rest
• Keys can be revoked at any time from the dashboard
• Use environment variables to store keys — never hardcode them in source code
• For browser-based applications, use a backend proxy to avoid exposing keys to the client