More work on MCP handlers. Changed the Validation handler.

tools/mcp-bridge.py

@@ -0,0 +1,165 @@
+#!/usr/bin/env python3
+"""
+MCP stdio-to-TCP bridge for BlueprintMCP.
+
+Reads JSON-RPC messages from stdin, forwards them to the BlueprintMCP TCP server,
+and writes responses to stdout. If the editor isn't running, returns valid MCP
+error responses instead of crashing.
+"""
+
+import sys
+import json
+import socket
+import time
+
+HOST = "localhost"
+PORT = 9847
+CONNECT_TIMEOUT = 2
+READ_TIMEOUT = 120
+
+sock = None
+
+
+def connect():
+    """Try to connect to the editor. Returns True on success."""
+    global sock
+    if sock is not None:
+        return True
+    try:
+        s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+        s.settimeout(CONNECT_TIMEOUT)
+        s.connect((HOST, PORT))
+        s.settimeout(READ_TIMEOUT)
+        sock = s
+        return True
+    except (ConnectionRefusedError, socket.timeout, OSError):
+        return False
+
+
+def disconnect():
+    global sock
+    if sock is not None:
+        try:
+            sock.close()
+        except Exception:
+            pass
+        sock = None
+
+
+def send_and_receive(message):
+    """Send a JSON-RPC message to the editor and return the response."""
+    data = json.dumps(message) + "\n"
+    sock.sendall(data.encode())
+
+    result = b""
+    while True:
+        chunk = sock.recv(65536)
+        if not chunk:
+            raise ConnectionError("Connection closed")
+        result += chunk
+        try:
+            return json.loads(result)
+        except json.JSONDecodeError:
+            continue
+
+
+def editor_down_response(msg):
+    """Return a valid MCP error response indicating the editor is down."""
+    msg_id = msg.get("id", 0)
+    method = msg.get("method", "")
+
+    if method == "initialize":
+        return {
+            "jsonrpc": "2.0",
+            "id": msg_id,
+            "result": {
+                "protocolVersion": "2024-11-05",
+                "capabilities": {"tools": {}},
+                "serverInfo": {"name": "blueprint-mcp", "version": "1.0.0"},
+                "_notice": "Unreal Editor is not running. No tools are available. Start the editor and restart Claude Code.",
+            },
+        }
+
+    if method == "notifications/initialized":
+        return None  # No response needed for notifications
+
+    if method == "tools/list":
+        return {
+            "jsonrpc": "2.0",
+            "id": msg_id,
+            "result": {
+                "tools": [{
+                    "name": "editor_not_running",
+                    "description": "Unreal Editor is not running. Start the editor and restart Claude Code to get BlueprintMCP tools.",
+                    "inputSchema": {"type": "object", "properties": {}},
+                }],
+            },
+        }
+
+    if method == "tools/call":
+        return {
+            "jsonrpc": "2.0",
+            "id": msg_id,
+            "result": {
+                "content": [
+                    {"type": "text", "text": json.dumps({"error": "Unreal Editor is down."})}
+                ],
+                "isError": True,
+            },
+        }
+
+    return {
+        "jsonrpc": "2.0",
+        "id": msg_id,
+        "error": {"code": -32000, "message": "Unreal Editor is down."},
+    }
+
+
+def handle_message(msg):
+    """Handle one JSON-RPC message. Try the editor first, fall back to offline responses."""
+    method = msg.get("method", "")
+
+    # Notifications don't get responses
+    if "id" not in msg:
+        if connect():
+            try:
+                sock.sendall((json.dumps(msg) + "\n").encode())
+            except Exception:
+                disconnect()
+        return None
+
+    # Try connecting (or reconnecting) to the editor
+    if not connect():
+        return editor_down_response(msg)
+
+    try:
+        return send_and_receive(msg)
+    except Exception:
+        disconnect()
+        # Retry once in case the connection was stale
+        if connect():
+            try:
+                return send_and_receive(msg)
+            except Exception:
+                disconnect()
+        return editor_down_response(msg)
+
+
+def main():
+    for line in sys.stdin:
+        line = line.strip()
+        if not line:
+            continue
+        try:
+            msg = json.loads(line)
+        except json.JSONDecodeError:
+            continue
+
+        response = handle_message(msg)
+        if response is not None:
+            sys.stdout.write(json.dumps(response) + "\n")
+            sys.stdout.flush()
+
+
+if __name__ == "__main__":
+    main()