// legacy-sse-harness.js
const BASE_URL = "https://mcp.brilliantdirectories.com";

async function run() {
  const sseResp = await fetch(`${BASE_URL}/sse`, {
    method: "GET",
    headers: { accept: "text/event-stream" },
  });
  if (!sseResp.ok) { console.log("FAIL:", sseResp.status); process.exit(1); }

  const reader = sseResp.body.getReader();
  const decoder = new TextDecoder();
  let buffer = "", endpoint = null;

  while (true) {
    const { value, done } = await reader.read();
    if (done) break;
    buffer += decoder.decode(value, { stream: true });

    let frameEnd;
    while ((frameEnd = buffer.indexOf("\n\n")) !== -1) {
      const frame = buffer.slice(0, frameEnd);
      buffer = buffer.slice(frameEnd + 2);
      const lines = frame.split("\n");
      let event = "message", data = "";
      for (const line of lines) {
        if (line.startsWith("event:")) event = line.slice(6).trim();
        else if (line.startsWith("data:")) data += line.slice(5).trim();
      }

      if (event === "endpoint" && !endpoint) {
        endpoint = data;
        const postUrl = new URL(endpoint, BASE_URL).toString();
        fetch(postUrl, {
          method: "POST",
          headers: { "content-type": "application/json" },
          body: JSON.stringify({ jsonrpc: "2.0", id: 1, method: "tools/list" }),
        }).catch(() => {});
      } else if (event === "message") {
        const parsed = JSON.parse(data);
        if (parsed.result?.tools) {
          console.log(`PASS — ${parsed.result.tools.length} tools`);
          process.exit(0);
        }
      }
    }
  }
}
run();

GET /sse HTTP 200, content-type=text/event-stream
<-- frame event="endpoint" data=/messages?sessionId=4f8b3f16-...
--> POST https://mcp.brilliantdirectories.com/messages?sessionId=...
POST /messages HTTP 202
<-- frame event="message" data={"jsonrpc":"2.0","id":1,"result":{"tools":[...
PASS — 173 tools, 172ms total

const BASE_URL = "https://mcp.brilliantdirectories.com";

async function run() {
  const sseResp = await fetch(`${BASE_URL}/sse`, {
    method: "GET",
    headers: { accept: "text/event-stream" },
  });
  if (!sseResp.ok) { console.log("FAIL:", sseResp.status); process.exit(1); }

  const reader = sseResp.body.getReader();
  const decoder = new TextDecoder();
  let buffer = "", endpoint = null;

  while (true) {
    const { value, done } = await reader.read();
    if (done) break;
    buffer += decoder.decode(value, { stream: true });

    let frameEnd;
    while ((frameEnd = buffer.indexOf("\n\n")) !== -1) {
      const frame = buffer.slice(0, frameEnd);
      buffer = buffer.slice(frameEnd + 2);
      const lines = frame.split("\n");
      let event = "message", data = "";
      for (const line of lines) {
        if (line.startsWith("event:")) event = line.slice(6).trim();
        else if (line.startsWith("data:")) data += line.slice(5).trim();
      }
      if (event === "endpoint" && !endpoint) {
        endpoint = data;
        const postUrl = new URL(endpoint, BASE_URL).toString();
        fetch(postUrl, {
          method: "POST",
          headers: { "content-type": "application/json" },
          body: JSON.stringify({ jsonrpc: "2.0", id: 1, method: "tools/list" }),
        }).catch(() => {});
      } else if (event === "message") {
        const parsed = JSON.parse(data);
        if (parsed.result?.tools) {
          console.log(`PASS — ${parsed.result.tools.length} tools`);
          process.exit(0);
        }
      }
    }
  }
}
run();


### Expected behavior

The MCP Client Tool's Tool dropdown should populate with tools advertised by the external MCP server's `tools/list` response. When pointed at a spec-compliant MCP server (one that passes MCP Inspector), the node should:

1. Open the SSE stream (for SSE transport) or complete the Streamable HTTP `initialize` handshake (for HTTP Streamable transport)
2. Send a `tools/list` JSON-RPC request
3. Populate the Tool dropdown from the response

**Observed against the same URL in other MCP clients:**

- ✅ **MCP Inspector** (official reference implementation): successful, 173 tools listed
- ✅ **Claude Desktop** (remote MCP): successful
- ✅ **Cursor** (remote MCP): successful
- ✅ **Claude Code CLI**: successful
- ✅ **Windsurf, Cline**: successful
- ✅ **Direct curl JSON-RPC POST**: successful
- ✅ **Standalone Node.js SSE handshake harness** (included in the reproduction steps): successful in ~170ms
- ❌ **n8n MCP Client Tool**: fails in ~1 second with no outbound HTTP traffic

**Expected:** n8n's MCP Client Tool node should connect successfully, as the server is verified spec-compliant and publicly reachable.


### Debug Info

# Debug info

## core

- n8nVersion: 2.17.3
- platform: docker (cloud)
- nodeJsVersion: 24.14.1
- nodeEnv: production
- database: sqlite
- executionMode: regular
- concurrency: 5
- license: enterprise (sandbox)
- consumerId: 00000000-0000-0000-0000-000000000000

## storage

- success: all
- error: all
- progress: false
- manual: true
- binaryMode: filesystem

## pruning

- enabled: true
- maxAge: 168 hours
- maxCount: 2500 executions

## client

- userAgent: mozilla/5.0 (windows nt 10.0; win64; x64; rv:150.0) gecko/20100101 firefox/150.0
- isTouchDevice: false

Generated at: 2026-04-22T22:00:31.214Z

### Operating System

Windows 10

### n8n Version

n8n website

### Node.js Version

n/a

### Database

SQLite (default)

### Execution mode

main (default)

### Hosting

n8n cloud