From 5de59f92363e1b0c02152df8e91af4bbbb185861 Mon Sep 17 00:00:00 2001
From: William FH <13333726+hinthornw@users.noreply.github.com>
Date: Tue, 23 Jan 2024 07:54:47 -0800
Subject: [PATCH] Core[Patch] Parse tool input after on_start (#16430)

For tracing, if a validation error occurs, currently it is attributed to
the previous step of the chain. It would be nice to have the on_start
and on_error callbacks called for tools when there is a validation error
that occurs to more easily attribute the root-cause
---
 libs/core/langchain_core/tools.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/libs/core/langchain_core/tools.py b/libs/core/langchain_core/tools.py
index b83a5cc8a7..a536da4c79 100644
--- a/libs/core/langchain_core/tools.py
+++ b/libs/core/langchain_core/tools.py
@@ -312,7 +312,6 @@ class ChildTool(BaseTool):
         **kwargs: Any,
     ) -> Any:
         """Run the tool."""
-        parsed_input = self._parse_input(tool_input)
         if not self.verbose and verbose is not None:
             verbose_ = verbose
         else:
@@ -341,6 +340,7 @@ class ChildTool(BaseTool):
             **kwargs,
         )
         try:
+            parsed_input = self._parse_input(tool_input)
             tool_args, tool_kwargs = self._to_args_and_kwargs(parsed_input)
             observation = (
                 self._run(*tool_args, run_manager=run_manager, **tool_kwargs)
@@ -392,7 +392,6 @@ class ChildTool(BaseTool):
         **kwargs: Any,
     ) -> Any:
         """Run the tool asynchronously."""
-        parsed_input = self._parse_input(tool_input)
         if not self.verbose and verbose is not None:
             verbose_ = verbose
         else:
@@ -416,6 +415,7 @@ class ChildTool(BaseTool):
             **kwargs,
         )
         try:
+            parsed_input = self._parse_input(tool_input)
             # We then call the tool on the tool input to get an observation
             tool_args, tool_kwargs = self._to_args_and_kwargs(parsed_input)
             observation = (