setting GOOGLE_CLOUD_QUOTA_PROJECT creates error with bigquery built-in tool

[pratapram]

Describe the bug
This is related to adk-python. When I set the GOOGLE_CLOUD_QUOTA_PROJECT environment variable when using the bigquery built-in tool I get this error

"I am sorry, but I cannot fulfill this request. The tool is consistently returning an authorization error, preventing me from executing the necessary SQL query to find out who the reviewers of tps documents are. Please ensure that the authorization to access Google services for execute_sql is completed."

To Reproduce
Steps to reproduce the behavior:

1. Create an agent with bigquery-builtin tool

2. run the agent and trigger this tool call

3. See error
   "I am sorry, but I cannot fulfill this request. The tool is consistently returning an authorization error, preventing me from executing the necessary SQL query to find out who the reviewers of tps documents are. Please ensure that the authorization to access Google services for execute_sql is completed."

4. Workaround:
   Expected behavior
   There was a annoying warning about how it needs a "quota project". I tried to add this environment variable to remove that warning, but surprisingly the bigquery-builtin tool authentication fails after adding this. It took me 2 days to root cause this error to the one line of configuration. This configuration seems unrelated to authentication. Removing this environment variable (GOOGLE_CLOUD_QUOTA_PROJECT) completely eliminated the problem.

Desktop (please complete the following information):

• OS: macos
• Python version(python -V): Python 3.12.8
• ADK version(pip show google-adk): Version: 1.12.0

Model Information:
Gemini-2.5-pro

Additional context
Bigquery builtin tool
https://google.github.io/adk-docs/tools/built-in-tools/#bigquery

[shobsi]

@pratapram thanks for reporting this issue. Could you please share following details for us to debug this further:

1. Are you setting any credentials for the BQ tools? If yes, what kind (examples)?
2. What kind of error you saw related to how it needs a "quota project"? Could you paste the full error string (redacting any sensitive information)?
3. You root caused this error to the which one line of configuration?