gh-jezweb-claude-skills-skills-cloudflare-mcp-server/references/transport.md

MCP Transport Methods - SSE vs Streamable HTTP

Comparison of the two MCP transport protocols supported by Cloudflare.

---

Quick Comparison

Feature	SSE	Streamable HTTP
Status	Legacy	Current (2025)
Efficiency	Lower	Higher
Adoption	High (all clients)	Low (new clients)
Endpoint	/sse	/mcp
Method	serveSSE()	serve()
Recommendation	Support both	Support both

---

SSE (Server-Sent Events)

Overview

• Original MCP transport
• Uses HTTP + Server-Sent Events
• Widely supported by all MCP clients

Implementation

MyMCP.serveSSE("/sse").fetch(request, env, ctx)

Client Configuration

{
  "mcpServers": {
    "my-mcp": {
      "url": "https://my-mcp.workers.dev/sse"
    }
  }
}

Pros

✅ Supported by all MCP clients ✅ Established protocol ✅ Works everywhere

Cons

❌ Less efficient ❌ Higher latency ❌ More bandwidth

---

Streamable HTTP

Overview

• New MCP transport (2025)
• Uses HTTP with streaming
• More efficient, lower latency

Implementation

MyMCP.serve("/mcp").fetch(request, env, ctx)

Client Configuration

{
  "mcpServers": {
    "my-mcp": {
      "url": "https://my-mcp.workers.dev/mcp"
    }
  }
}

Pros

✅ More efficient ✅ Lower latency ✅ Less bandwidth ✅ Better error handling

Cons

❌ Not all clients support yet ❌ Newer standard

---

Supporting Both (Recommended)

export default {
  fetch(request: Request, env: Env, ctx: ExecutionContext) {
    const { pathname } = new URL(request.url);

    if (pathname.startsWith("/sse")) {
      return MyMCP.serveSSE("/sse").fetch(request, env, ctx);
    }

    if (pathname.startsWith("/mcp")) {
      return MyMCP.serve("/mcp").fetch(request, env, ctx);
    }

    return new Response("Not Found", { status: 404 });
  }
};

Why support both?

• Maximum client compatibility
• Smooth transition as clients upgrade
• No breaking changes

---

With OAuth

import { OAuthProvider } from "@cloudflare/workers-oauth-provider";

export default new OAuthProvider({
  // ... OAuth config ...

  apiHandlers: {
    "/sse": MyMCP.serveSSE("/sse"),
    "/mcp": MyMCP.serve("/mcp")
  }
});

---

Testing

Test SSE

npx @modelcontextprotocol/inspector@latest
# Enter: http://localhost:8788/sse

Test Streamable HTTP

# Use mcp-remote adapter
npx mcp-remote http://localhost:8788/mcp

---

Recommendation: Support both transports for maximum compatibility.