MCP vs REST vs WebSocket for NinjaTrader Automation

Pick by who is making the call

• REST: your application code knows exactly what it wants. Request/response, idempotent, deterministic, cacheable.
• WebSocket: your application code wants to react to events. Streaming, low-latency, push.
• MCP: an AI model is choosing which call to make next based on conversation. Typed tools, OAuth-scoped, agent-friendly.

When REST is the right answer

• You are writing a Python or JS script that places an order on a schedule.
• You are integrating with a third-party CRM or accounting system that does request/response.
• You want a typed OpenAPI surface to generate clients in your language.
• You need predictable rate limits and retries.

See CrossTrade API Overview for endpoints, auth, and rate-limit details. Pro tier and above.

When WebSocket is the right answer

• You need quote updates without polling.
• You are building a custom dashboard that reacts to fills and account state.
• You want event-driven copier or alert handling.

See WebSocket API docs. Pro tier and above.

When MCP is the right answer

• An AI assistant (Claude, ChatGPT, Cursor) is the user-facing surface.
• You want the model to choose tools based on the conversation.
• You want OAuth-scoped permissions (mcp:read vs mcp:trade) instead of hand-rolled auth.
• You need access to MCP-only Elite tools: NinjaScript compile, Strategy Analyzer backtest parity, deployment registry, webhook signal history, journal, copier activity.

See MCP Trading API. Elite tier.

Side by side

Place a limit order on MES 06-26

REST

POST /v1/api/accounts/Sim101/orders/place
Authorization: Bearer <PAT>
Content-Type: application/json

{ "instrument": "MES 06-26", "side": "Buy", "type": "Limit",
  "quantity": 1, "limit_price": 5230.00, "tif": "Day" }

WebSocket (subscribe to fills)

// Place via REST, then listen to fills.
ws.subscribe("/v1/ws/accounts/Sim101/executions")

MCP

Agent: "On Sim101, place a buy limit for 1 MES 06-26 at 5230.00, day order.
Restate and wait for me to confirm before calling."

User: confirm.

Agent: [calls PlaceOrder]

Same outcome, three audiences. REST for code. WebSocket for streaming. MCP for an AI conversation.

What each surface needs

The Elite tier specifically gates the MCP transport. REST and WebSocket remain on Pro.

Different approval models

• REST/WebSocket: your code is the human-in-the-loop. You ship the safety logic.
• MCP: the conversation is the interface; the agent's prompt encodes approval gates. The OAuth scope is a hard floor.

Frequently asked questions