feat: Add custom User-Agent header to RestApiTool requests

[rcsantana777]

This PR adds a custom User-Agent header to all requests made via RestApiTool. This allows backend services to identify traffic originating from the ADK. The header format is google-adk/<version> (tool: <tool_name>), where <version> is the current version of the google-adk package, fetched dynamically from google.adk.version, and <tool_name> is the name of the specific RestApiTool instance.

Associated Issue

Fixes #2676

Testing Plan

Unit Tests

I ran the full suite of unit tests locally to ensure the changes did not introduce any regressions. All tests passed successfully.

$ pytest ./tests/unittests
================================= 4202 passed, 2459 warnings in 44.68s ====================

The warnings are related to existing experimental features and are not affected by this change.

Manual End-to-End (E2E) Test

I performed a manual test to ensure the integrated flow works as expected.

• Setup: Created a clean virtual environment (~/venvs/adk-e2e-test) and installed the locally built google-adk package using uv venv --seed and pip install dist/google_adk-*.whl. Ran a custom mock_server.py script (using Flask) in one terminal to listen for requests and print headers. Ran a custom run_test_tool.py script in a second terminal to send a request using the modified RestApiTool.

• Execution: The run_test_tool.py script successfully sent a POST request to the mock server's /test endpoint. The mock server received the request and printed the headers.

  run_test_tool.py Output:

  {
    "message": "Request received successfully!"
  }

  mock_server.py Output (Headers):

  --- Request Received ---
  Headers:
    Host: 127.0.0.1:8000
    User-Agent: google-adk/1.12.0 (tool: TestTool)
    Accept-Encoding: gzip, deflate
    Accept: */*
    Connection: keep-alive
    Content-Type: application/json
    Content-Length: 2
  ------------------------
  

  The User-Agent: google-adk/1.12.0 (tool: TestTool) header confirms the change is working as intended, dynamically fetching the package version and including the tool name.

Checklist

• Associated issue linked
• Unit tests passed
• End-to-end test performed and results documented
• Code formatted with ./autoformat.sh

---

[gemini-code-assist]

Summary of Changes

Hello @rcsantana777, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request introduces a new feature to enhance the traceability of API requests originating from the ADK. By adding a custom User-Agent header to all requests made via the RestApiTool, backend services will now be able to identify and differentiate traffic coming from the ADK. This change is crucial for monitoring and analytics, providing better insights into the source of API calls.

Highlights

• User-Agent Header Addition: A custom User-Agent header, specifically "google-adk/1.0", has been implemented for all requests originating from the RestApiTool. This allows backend services to accurately identify traffic from the ADK.

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[adk-bot]

Response from ADK Triaging Agent

Hello @rcsantana777, thank you for creating this PR!

To help reviewers evaluate your contribution more efficiently, could you please address the following points from our contribution guidelines?

• Associated Issue: All PRs, other than small documentation or typo fixes, should have an issue associated with them. If one doesn't exist, could you please create one and link it here?
• Testing Plan: Please include a testing plan section in your PR description to detail how you have tested these changes.

Thank you!

[gemini-code-assist]

Code Review

This pull request adds a custom User-Agent header to requests made via RestApiTool. The change is good for identifying traffic from the ADK. My feedback focuses on improving maintainability by replacing the hardcoded User-Agent string with a constant and cleaning up the code formatting for better readability.

[seanzhou1023]

could you please run ./autoformat.sh to format your changes ? Check Pyink Formatting / pyink-check (pull_request) failed