diff --git a/gns3server/api/routes/mcp/__init__.py b/gns3server/api/routes/mcp/__init__.py
index 3cbc66b64..39d19a501 100644
--- a/gns3server/api/routes/mcp/__init__.py
+++ b/gns3server/api/routes/mcp/__init__.py
@@ -44,6 +44,7 @@ from mcp.server.transport_security import TransportSecuritySettings
 
 from gns3server.config import Config
 from gns3server.services import auth_service
+from gns3server.utils.request_utils import extract_client_info
 from .projects import (
     list_projects_handler, get_project_handler, create_project_handler,
     delete_project_handler, open_project_handler, close_project_handler,
@@ -70,6 +71,59 @@ from .computes import (
 log = logging.getLogger(__name__)
 
 
+# ── Server ready state ────────────────────────────────────────────────
+# Tracks whether GNS3 server has completed initialization.
+# MCP connections wait up to 5 seconds for startup to complete, then return
+# 503 Service Unavailable if initialization is not complete to prevent
+# "Received request before initialization was complete" errors.
+
+_mcp_ready_event = asyncio.Event()
+
+
+def set_mcp_server_ready(ready: bool = True) -> None:
+    """
+    Set MCP server ready state.
+
+    Should be called after GNS3 startup completes (database, controller, etc.)
+    to allow MCP connections to proceed.
+
+    Args:
+        ready: True to mark server as ready, False to mark as not ready
+    """
+    if ready:
+        _mcp_ready_event.set()
+        log.info("MCP server is now ready to accept connections")
+    else:
+        _mcp_ready_event.clear()
+
+
+async def wait_for_mcp_ready() -> bool:
+    """
+    Wait until MCP server is ready before accepting connections.
+
+    Returns:
+        True if server is ready, False if timeout reached
+
+    Returns immediately if already ready. Otherwise waits with a timeout
+    and returns False if server does not become ready in time.
+    """
+    if _mcp_ready_event.is_set():
+        return True
+
+    log.debug("MCP server not ready yet, waiting for initialization to complete...")
+
+    try:
+        await asyncio.wait_for(_mcp_ready_event.wait(), timeout=5.0)
+        log.debug("MCP server is now ready, proceeding with connection")
+        return True
+    except asyncio.TimeoutError:
+        log.warning(
+            "MCP server ready check timed out after 5 seconds - "
+            "GNS3 server initialization may have issues"
+        )
+        return False
+
+
 # ── Per‑connection JWT token  ─────────────────────────────────────────
 # Set during SSE authentication, read by tool handlers running in the
 # same asyncio task (contextvars propagate through asyncio.to_thread).
@@ -485,6 +539,22 @@ def _make_auth_wrapper(inner_app):
     """
 
     async def auth_wrapper(scope, receive, send):
+        # Wait for GNS3 server to complete initialization before accepting MCP connections
+        server_ready = await wait_for_mcp_ready()
+        if not server_ready:
+            # Server initialization timed out - return 503 Service Unavailable
+            client_info = extract_client_info(scope, auth_service)
+            log.warning(
+                f"Rejecting MCP connection - GNS3 server initialization not complete. "
+                f"Client: {client_info['host']}:{client_info['port']} ({client_info['user_info']}, Path: {client_info['path']})"
+            )
+            response = Response(
+                "GNS3 server initialization not complete - please retry later",
+                status_code=503
+            )
+            await response(scope, receive, send)
+            return
+
         if scope["type"] == "http" and scope["method"] == "GET":
             token = None
             headers = dict(scope.get("headers", []))
diff --git a/gns3server/core/tasks.py b/gns3server/core/tasks.py
index 99ab6c122..08afc2198 100644
--- a/gns3server/core/tasks.py
+++ b/gns3server/core/tasks.py
@@ -84,6 +84,11 @@ async def startup(app: FastAPI) -> None:
         m = module.instance()
         m.port_manager = PortManager.instance()
 
+    # Mark MCP server as ready to accept connections
+    from gns3server.api.routes.mcp import set_mcp_server_ready
+    set_mcp_server_ready(True)
+    log.info("GNS3 server startup completed")
+
 
 async def shutdown(app: FastAPI) -> None:
     """
diff --git a/gns3server/utils/request_utils.py b/gns3server/utils/request_utils.py
new file mode 100644
index 000000000..aee3bdb2e
--- /dev/null
+++ b/gns3server/utils/request_utils.py
@@ -0,0 +1,91 @@
+"""
+Utilities for extracting request information from ASGI scope.
+
+This module provides reusable functions for extracting client information
+from ASGI scope dictionaries for logging and debugging purposes.
+"""
+
+import logging
+from urllib.parse import parse_qs
+from typing import Dict, Any, Optional
+
+log = logging.getLogger(__name__)
+
+
+def extract_client_info(scope: Dict[str, Any], auth_service_instance: Optional[Any] = None) -> Dict[str, str]:
+    """
+    Extract client information from ASGI scope for logging purposes.
+
+    Args:
+        scope: ASGI scope dictionary containing request metadata
+        auth_service_instance: Optional auth service instance for token validation
+
+    Returns:
+        Dictionary with client information:
+        - host: Client IP address
+        - port: Client port
+        - path: Request path
+        - method: Request method
+        - username: Authenticated username (if token provided and valid)
+        - user_info: Human-readable user info string
+    """
+    # Extract client address and port
+    client = scope.get("client", (None, None))
+    client_host = client[0] if client and client[0] else "unknown"
+    client_port = str(client[1]) if client and len(client) > 1 else "unknown"
+
+    # Extract request info
+    path = scope.get("path", "unknown")
+    method = scope.get("method", "unknown")
+
+    # Try to extract username from token
+    username = None
+    if auth_service_instance:
+        try:
+            headers = dict(scope.get("headers", []))
+            auth = headers.get(b"authorization", b"").decode()
+            token = None
+
+            # Try Authorization header
+            if auth.startswith("Bearer "):
+                token = auth[7:]
+
+            # Try query parameter
+            if not token:
+                params = parse_qs(scope.get("query_string", b"").decode())
+                tokens = params.get("token", [])
+                if tokens:
+                    token = tokens[0]
+
+            # Validate and extract username
+            if token:
+                username = auth_service_instance.get_username_from_token(token)
+        except Exception as e:
+            log.debug(f"Failed to extract username from token: {e}")
+            username = None
+
+    # Create user-friendly info string
+    user_info = f"user '{username}'" if username else "unauthenticated user"
+
+    return {
+        "host": client_host,
+        "port": client_port,
+        "path": path,
+        "method": method,
+        "username": username,
+        "user_info": user_info
+    }
+
+
+def format_client_log(client_info: Dict[str, str], message: str) -> str:
+    """
+    Format a log message with client information.
+
+    Args:
+        client_info: Client information dict from extract_client_info()
+        message: Log message
+
+    Returns:
+        Formatted log string with client prefix
+    """
+    return f"{message} - Client: {client_info['host']}:{client_info['port']} ({client_info['user_info']}, Path: {client_info['path']})"