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find_context_parameter fails to detect context-typed parameters with postponed annotations #4754
Description
Describe the Bug:
If a tool function is defined in a module that uses from __future__ import annotations, ADK can fail to recognize Context / ToolContext parameters because find_context_parameter() looks at the raw annotation string instead of resolved type hints. When that happens, find_context_parameter() misses the real context parameter. FunctionTool then falls back to the literal name tool_context, so a custom-named context parameter like ctx is not excluded from declaration building and eventually triggers a misleading ValueError saying it must be named tool_context. This is easy to miss because a parameter already named tool_context happens to match the fallback and masks the bug.
Steps to Reproduce:
- Install google-adk from source (main branch)
- Create a file with the following code:
from __future__ import annotations
from google.adk.tools.function_tool import FunctionTool
from google.adk.tools.tool_context import ToolContext
def my_tool(query: str, ctx: ToolContext) -> str:
"""A tool that searches for something."""
return f"Result for {query}"
tool = FunctionTool(my_tool)
print(tool._get_declaration())- Run the file with
uv run python my_tool.py
Expected Behavior:
The tool should be created successfully with ctx excluded from the schema, identical to the behavior without from __future__ import annotations
Observed Behavior:
ValueError: `ToolContext` parameter must be named as `tool_context`. Found `ctx` instead in function `my_tool`.
Environment Details:
- ADK Library Version (pip show google-adk): 1.26.0
- Desktop OS: Windows 11
- Python Version (python -V): 3.10.19
Activity
surajksharma07 commentedon Mar 8, 2026
@gautamvarmadatla Thanks for the detailed report and for already putting up PR #4755 — the root cause is spot on:
find_context_parameter()uses an identity check (annotation is Context) that breaks whenfrom __future__ import annotationsturns annotations into strings.As an immediate workaround until the PR lands, renaming the context parameter to
tool_contextwill unblock you sinceFunctionToolfalls back to that name — could you confirm if that works for your case in the meantime?Once you've validated the fix in PR #4755 holds up across your use cases, it'd be great to get that reviewed and merged.
Team is looking more into it.
gautamvarmadatla commentedon Mar 8, 2026
hi @surajksharma07, thanks so much for the prompt response.
I’ve been testing locally with the same patch as in #4755, and it seems to be working on my end.
surajksharma07 commentedon Mar 8, 2026
@gautamvarmadatla Good to hear the patch in #4755 is working on your end — that confirms the fix is on the right track.
We'll move ahead with the PR review; once it's been looked at on our side, we'll get it merged in.
Team is looking more into it.
Thanks!
surajksharma07 commentedon Mar 8, 2026
@xuanyang15 Please have a look into it.
xuanyang15 commentedon Mar 26, 2026
Covered by 22fc332
fix: build function declaration when a param uses a TYPE_CHECKING-onl…
fix: build function declaration when a param uses a TYPE_CHECKING-onl…
fix: build function declaration when a param uses a TYPE_CHECKING-onl…