Protocol for MCP handler revised.

tools/mcp-bridge.py

@@ -2,21 +2,42 @@
 """
 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.
+Exposes a single MCP tool "unreal" that forwards JSON commands to the
+BlueprintMCP TCP server in the Unreal Editor. The tool list is static,
+so it works regardless of whether the editor is running at startup.
 """
 
 import sys
 import json
 import socket
-import time
 
 HOST = "localhost"
 PORT = 9847
 CONNECT_TIMEOUT = 2
 READ_TIMEOUT = 120
 
+TOOL_DESCRIPTION = (
+    "Send a command to the Unreal Editor's BlueprintMCP plugin. "
+    "The 'command' field specifies which operation to perform; "
+    "additional fields are command-specific parameters. "
+    'Use {"command": "show_commands"} to list available commands. '
+    "If the editor is not running, the call will return an error; "
+    "just ask the user to start the editor and try again."
+)
+
+TOOL_SCHEMA = {
+    "name": "unreal",
+    "description": TOOL_DESCRIPTION,
+    "inputSchema": {
+        "type": "object",
+        "properties": {
+            "command": {"type": "string", "description": "The command to execute"},
+        },
+        "required": ["command"],
+        "additionalProperties": True,
+    },
+}
+
 sock = None
 
 
@@ -47,7 +68,7 @@ def disconnect():
 
 
 def send_and_receive(message):
-    """Send a JSON-RPC message to the editor and return the response."""
+    """Send a JSON message to the editor and return the response."""
     data = json.dumps(message) + "\n"
     sock.sendall(data.encode())
 
@@ -63,86 +84,61 @@ def send_and_receive(message):
             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
+def forward_to_editor(arguments):
+    """Forward arguments to the editor, return the result dict."""
     if not connect():
-        return editor_down_response(msg)
-
+        return {"error": "Unreal Editor is not running. Start the editor and try again."}
     try:
-        return send_and_receive(msg)
+        return send_and_receive(arguments)
     except Exception:
         disconnect()
         # Retry once in case the connection was stale
         if connect():
             try:
-                return send_and_receive(msg)
+                return send_and_receive(arguments)
             except Exception:
                 disconnect()
-        return editor_down_response(msg)
+        return {"error": "Lost connection to Unreal Editor."}
+
+
+def make_jsonrpc(msg_id, result):
+    return {"jsonrpc": "2.0", "id": msg_id, "result": result}
+
+
+def handle_message(msg):
+    """Handle one JSON-RPC message from Claude Code."""
+    msg_id = msg.get("id")
+    method = msg.get("method", "")
+
+    # Notifications don't get responses
+    if msg_id is None:
+        return None
+
+    if method == "initialize":
+        return make_jsonrpc(msg_id, {
+            "protocolVersion": "2024-11-05",
+            "capabilities": {"tools": {}},
+            "serverInfo": {"name": "blueprint-mcp", "version": "1.0.0"},
+        })
+
+    if method == "tools/list":
+        return make_jsonrpc(msg_id, {"tools": [TOOL_SCHEMA]})
+
+    if method == "tools/call":
+        params = msg.get("params", {})
+        arguments = params.get("arguments", {})
+        result = forward_to_editor(arguments)
+        is_error = "error" in result
+        return make_jsonrpc(msg_id, {
+            "content": [{"type": "text", "text": json.dumps(result)}],
+            **({"isError": True} if is_error else {}),
+        })
+
+    return {
+        "jsonrpc": "2.0",
+        "id": msg_id,
+        "error": {"code": -32601, "message": f"Method not found: {method}"},
+    }
 
 
 def main():

tools/mcp-bridge.sh

@@ -1,2 +0,0 @@
-#!/bin/bash
-exec /usr/bin/nc localhost 9847