MCP OAuth Mode

The Euler Stream MCP server supports two mutually exclusive authentication modes for tool calls that require user identity. These two modes are XOR — you must choose one or the other per connection.

Authentication Modes

• OAuth Mode — The server requires an OAuth access token obtained through the Euler OAuth flow. The server itself handles the login flow.
• Cookie Mode (default) — The caller supplies raw TikTok cookies directly via the x-cookie-header parameter. No OAuth login is required.

URL Format

The authentication mode is determined by the oauth query parameter on the MCP endpoint URL. This is set at connection time, not per tool call.

# OAuth mode
https://<host>/mcp?oauth=true&apiKey=YOUR_API_KEY

# Cookie mode (default)
https://<host>/mcp?apiKey=YOUR_API_KEY

OAuth Mode (oauth=true)

When oauth=true is set on the MCP endpoint URL:

• The MCP server requires the OAuth login flow to be completed before tools can execute.
• Tools accept x-oauth-token — the access token from an authorized Euler OAuth app.
• The x-cookie-header parameter is not accepted and will be ignored.

Cookie Mode (default)

When oauth is omitted or set to false:

• No OAuth login flow is required to connect.
• Tools accept x-cookie-header — raw TikTok cookies for direct authentication.
• The x-oauth-token parameter is not accepted and will be ignored.

Using the Playground

Each tool's playground panel includes an OAuth Mode checkbox at the top. Toggling it:

• Updates the URL preview to show the endpoint with or without ?oauth=true, reflecting the selected server host.
• Enables the corresponding authentication field (x-oauth-token or x-cookie-header) and disables the other with a lock icon.
• When running a tool, the playground connects to the MCP server using the correct URL for the selected mode.

The URL preview always reflects the Server Host selected in the sidebar picker, so switching servers updates the preview automatically.

MCP Client Configuration

When configuring an external MCP client (Claude Desktop, Cursor, etc.), append ?oauth=true to the MCP endpoint URL to enable OAuth mode.

{
  "mcpServers": {
    "euler-stream": {
      "command": "npx",
      "args": [
        "mcp-remote",
        "https://<host>/mcp?oauth=true&apiKey=YOUR_API_KEY"
      ]
    }
  }
}

Pinning a User

When using OAuth mode, the authorization flow normally shows an account picker if the user has previously logged in. You can skip this step by passing pinned_user_id to the MCP endpoint URL, which automatically selects a specific TikTok user's cached session:

https://<host>/mcp?oauth=true&apiKey=YOUR_API_KEY&pinned_user_id=6779789250017592326

The pinned_user_id parameter is optional. If the user has a valid cached session, authorization completes instantly with no user interaction. If not found, the normal flow continues silently.

This is useful for MCP clients that manage a specific user context and want to avoid the account picker on reconnection.