Move invariant api key check to __main__.py so that the same check can work for both mcp and server commands.

gateway/__main__.py

@@ -10,6 +10,7 @@ import time
 from typing import Optional
 
 from gateway.mcp import mcp
+from gateway.mcp.log import mcp_log
 
 
 LOCAL_COMPOSE_FILE = "gateway/docker-compose.local.yml"
@@ -224,8 +225,18 @@ def main():
         sys.exit(1)
 
     verb = sys.argv[1]
+    if verb == "help":
+        print_help()
+        return 0
+
+    if "INVARIANT_API_KEY" not in os.environ:
+        print("[ERROR] INVARIANT_API_KEY environment variable is not set.")
+        mcp_log("[ERROR] INVARIANT_API_KEY environment variable is not set.")
+        sys.exit(1)
+
     if verb == "mcp":
         return asyncio.run(mcp.execute(sys.argv[2:]))
+
     if verb == "server":
         if len(sys.argv) < 3:
             print(
@@ -239,9 +250,7 @@ def main():
         if not run_server_command(command, args):
             return 1
         return 0
-    if verb == "help":
-        print_help()
-        return 0
+
     print(f"[gateway/__main__.py] Unknown action: {verb}")
     return 1
 

gateway/mcp/README.md

@@ -67,6 +67,14 @@ Key Parameters
 
 *	--push-explorer: Enables pushing annotated traces of MCP message flows to the specified project in Invariant Explorer.
 
+### Logs
+
+To see logs and errors from the MCP gateway and the MCP server, you can do:
+
+```bash
+tail -f ~/.invariant/mcp.log
+```
+
 ### Local Development Workflow
 
 To test or develop the gateway locally:

gateway/mcp/mcp.py

@@ -464,10 +464,6 @@ def split_args(args: list[str] = None) -> tuple[list[str], list[str]]:
 
 async def execute(args: list[str] = None):
     """Main function to execute the MCP gateway."""
-    if "INVARIANT_API_KEY" not in os.environ:
-        mcp_log("[ERROR] INVARIANT_API_KEY environment variable is not set.")
-        sys.exit(1)
-
     mcp_gateway_args, mcp_server_command_args = split_args(args)
     ctx = McpContext(mcp_gateway_args)