Fix for Url Elicitation issue 1768 (#1780)

src/mcp/server/fastmcp/tools/base.py

@@ -11,6 +11,7 @@ from pydantic import BaseModel, Field
 from mcp.server.fastmcp.exceptions import ToolError
 from mcp.server.fastmcp.utilities.context_injection import find_context_parameter
 from mcp.server.fastmcp.utilities.func_metadata import FuncMetadata, func_metadata
+from mcp.shared.exceptions import UrlElicitationRequiredError
 from mcp.shared.tool_name_validation import validate_and_warn_tool_name
 from mcp.types import Icon, ToolAnnotations
 
@@ -108,6 +109,10 @@ class Tool(BaseModel):
                 result = self.fn_metadata.convert_result(result)
 
             return result
+        except UrlElicitationRequiredError:
+            # Re-raise UrlElicitationRequiredError so it can be properly handled
+            # as an MCP error response with code -32042
+            raise
         except Exception as e:
             raise ToolError(f"Error executing tool {self.name}: {e}") from e
 

src/mcp/server/lowlevel/server.py

@@ -90,7 +90,7 @@ from mcp.server.lowlevel.helper_types import ReadResourceContents
 from mcp.server.models import InitializationOptions
 from mcp.server.session import ServerSession
 from mcp.shared.context import RequestContext
-from mcp.shared.exceptions import McpError
+from mcp.shared.exceptions import McpError, UrlElicitationRequiredError
 from mcp.shared.message import ServerMessageMetadata, SessionMessage
 from mcp.shared.session import RequestResponder
 from mcp.shared.tool_name_validation import validate_and_warn_tool_name
@@ -569,6 +569,10 @@ class Server(Generic[LifespanResultT, RequestT]):
                             isError=False,
                         )
                     )
+                except UrlElicitationRequiredError:
+                    # Re-raise UrlElicitationRequiredError so it can be properly handled
+                    # by _handle_request, which converts it to an error response with code -32042
+                    raise
                 except Exception as e:
                     return self._make_error_result(str(e))