feat(mcp_server_manager.py): add static_header support for MCP's

Allow admin to configure static custom headers to send on each mcp request to a backend server

Closes LIT-1186

litellm/proxy/_experimental/mcp_server/mcp_server_manager.py

@@ -216,6 +216,7 @@ class MCPServerManager:
                 allowed_tools=server_config.get("allowed_tools", None),
                 disallowed_tools=server_config.get("disallowed_tools", None),
                 access_groups=server_config.get("access_groups", None),
+                static_headers=server_config.get("static_headers", None),
             )
             self.config_mcp_servers[server_id] = new_server
         verbose_logger.debug(
@@ -475,6 +476,11 @@ class MCPServerManager:
         client = None
 
         try:
+            if server.static_headers:
+                if extra_headers is None:
+                    extra_headers = {}
+                extra_headers.update(server.static_headers)
+
             client = self._create_mcp_client(
                 server=server,
                 mcp_auth_header=mcp_auth_header,
@@ -770,6 +776,11 @@ class MCPServerManager:
                 if header in raw_headers:
                     extra_headers[header] = raw_headers[header]
 
+        if mcp_server.static_headers:
+            if extra_headers is None:
+                extra_headers = {}
+            extra_headers.update(mcp_server.static_headers)
+
         client = self._create_mcp_client(
             server=mcp_server,
             mcp_auth_header=server_auth_header,

litellm/proxy/_new_secret_config.yaml

@@ -22,4 +22,5 @@ mcp_servers:
     transport: "http"
     description: "My custom MCP server"
     auth_type: "api_key"
-    auth_value: "abc123"
+    auth_value: "abc123"
+    static_headers: {"X-API-Key": "abc123"}

litellm/types/mcp_server/mcp_server_manager.py

@@ -21,7 +21,7 @@ class MCPServer(BaseModel):
     authentication_token: Optional[str] = None
     mcp_info: Optional[MCPInfo] = None
     extra_headers: Optional[List[str]] = (
-        None  # allow admin to specify which headers to forward to the MCP server
+        None  # allow admin to specify which headers to forward from client to the MCP server
     )
     allowed_tools: Optional[List[str]] = None
     disallowed_tools: Optional[List[str]] = None
@@ -36,4 +36,7 @@ class MCPServer(BaseModel):
     args: Optional[List[str]] = None
     env: Optional[Dict[str, str]] = None
     access_groups: Optional[List[str]] = None
+    static_headers: Optional[Dict[str, str]] = (
+        None  # static headers to forward to the MCP server
+    )
     model_config = ConfigDict(arbitrary_types_allowed=True)