[HhH666-ux]

Fixes #8035.

Problem

LangchainTool.__init__ only unwraps StructuredTool.func (the #707 fix). For a plain langchain_core.tools.Tool, the fallback lands on Tool._run(self, *args, config: RunnableConfig, ...), and FunctionTool.__init__ derives the function declaration from that signature — so the model sees a single required config parameter:

Tool declares: ['config'] required: ['config']
Tool run_async: {'error': 'Invoking `shout()` failed as the following mandatory input parameters are not present: config ...'}

while a StructuredTool built from the same function declares ['text'] and runs.

Changes

Before the generic fallback, unwrap a plain Tool's real callable:

if isinstance(tool, Tool) and getattr(tool, 'func', None) is not None:
  func = tool.func
elif hasattr(tool, '_run') or hasattr(tool, 'run'):
  ...

This mirrors the StructuredTool precedence (func first): the declaration is built from the user function's signature, and invocation goes through the same callable the StructuredTool path already uses. Scoped strictly to Tool instances — custom BaseTool subclasses that intentionally override _run keep the current behavior, and Tool(coroutine=...) without func is unchanged.

Verification

Offline, no API key (the issue's script, langchain-core 1.7.x):

• before: Tool(name="shout", func=shout) declares ['config'] required ['config']
• after: declares ['text'] required ['text'], matching the StructuredTool.from_function(shout) control

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[its-amann]

a plain Tool(func=None, coroutine=afn) still falls through to _run here, so it still declares config and then raises "Tool does not support sync invocation". the StructuredTool branch above already falls back to the coroutine, same thing works here

Suggested change

	if isinstance(tool, Tool) and getattr(tool, 'func', None) is not None:
	func = tool.func
	if isinstance(tool, Tool) and (tool.func or tool.coroutine) is not None:
	func = tool.func or tool.coroutine

fixed this with tests for both the sync and async plain Tool in this commit, you can just cherry pick it instead of redoing it: its-amann@5642875

[HhH666-ux]

Good catch — the func is not None check still landed on _run for Tool(func=None, coroutine=afn).

Pushed b29f889: the plain Tool branch now mirrors the StructuredTool one (tool.func or tool.coroutine), so an async-only plain Tool no longer advertises config or raises "Tool does not support sync invocation".

I took your test cases as-is (test_plain_tool_with_func / test_plain_tool_with_coroutine); all 12 tests in tests/unittests/integrations/langchain/test_langchain_tool.py pass locally. Thanks also for preparing the cherry-pick commit — much appreciated.

[chrikrah]

@HhH666-ux the func branch fixes the Tool(func=...) case from #8035, but I'd hold the merge for a test, since the 10 existing ones also pass on the base. blocking: its-amann's 5642875 adds that test plus the coroutine fallback you scoped out. Both tests fail on the base, and the coroutine one fails here too.

non-blocking: they check only the run_async result; asserting the declaration is ['text'] would pin what the model sees.

# git archive 912d7c6 and 5642875 (base 1cb926d), Python 3.12, langchain-core 1.7.6, pytest 9.2.0, langchain_tool.__file__ from the export
$ python repro.py   # the issue's script plus a coroutine-only Tool
head  Tool:            declares ['text'], run_async HI
head  Tool(coroutine): declares ['config'], run_async error: mandatory input parameters are not present: config
base  Tool:            declares ['config'], run_async error: mandatory input parameters are not present: config
$ python -m pytest -q tests/unittests/integrations/langchain/test_langchain_tool.py   # tests from 5642875, langchain_tool.py per row
base 1cb926d:  2 failed, 10 passed   # test_plain_tool_with_func, test_plain_tool_with_coroutine
head 912d7c6:  1 failed, 11 passed   # test_plain_tool_with_coroutine
5642875:       12 passed

Whichever branch ends up carrying 5642875, I'll rerun this there and approve.