diff --git a/src/agents/tool.py b/src/agents/tool.py
index 3aab47752..32dc38a0e 100644
--- a/src/agents/tool.py
+++ b/src/agents/tool.py
@@ -24,6 +24,7 @@
 from .items import RunItem
 from .logger import logger
 from .run_context import RunContextWrapper
+from .strict_schema import ensure_strict_json_schema
 from .tool_context import ToolContext
 from .tracing import SpanError
 from .util import _error_tracing
@@ -93,6 +94,10 @@ class FunctionTool:
     and returns whether the tool is enabled. You can use this to dynamically enable/disable a tool
     based on your context/state."""
 
+    def __post_init__(self):
+        if self.strict_json_schema:
+            self.params_json_schema = ensure_strict_json_schema(self.params_json_schema)
+
 
 @dataclass
 class FileSearchTool: