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[Bug]: Testing agent gives one service's tools inconsistent name prefixes, so the model calls names that don't exist

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Assessment

Difficulty
4/5
Estimated time
1-2 days
Newbie friendliness
55/100
Issue type
Bug
Clarity
Mostly clear
Activity status
Active
Tech stack
android, kotlin
Domain
backend-api-design

Research direction

Start by locating GeminiToolConverter.getGeminiFunctionName and trace how converted function names are matched when the Gemini provider receives a tool call; the report also names GeminiProviderImpl as a possible entry point. Reproduce with one service whose methods cross the 64-character cutoff at different points, then verify that its tools have consistent names or that calls resolve correctly; the issue provides no test file to run.

Written by the indexing model from the issue text.

Description

Description

The Testing Agent shortens each AppFunction id to a Gemini function name of at most 64 characters by keeping as many _-separated parts as fit, from the right (GeminiToolConverter.getGeminiFunctionName). Because the cutoff depends on each method's length, the tools of one service end up with different prefixes:

com.example.app.feature.notes.ExampleNotesAppFunctionService#addNote
  -> example_app_feature_notes_ExampleNotesAppFunctionService_addNote
com.example.app.feature.notes.ExampleNotesAppFunctionService#updateNoteSettings
  -> feature_notes_ExampleNotesAppFunctionService_updateNoteSettings
com.example.app.feature.notes.ExampleNotesAppFunctionService#getNoteFieldDescriptions
  -> notes_ExampleNotesAppFunctionService_getNoteFieldDescriptions

The model generalizes from the majority and "corrects" the others, so it calls names that don't exist, for example:

Called unknown function: feature_notes_ExampleNotesAppFunctionService_getNoteFieldDescriptions

We also saw a doubled prefix (the shortened prefix repeated in front of a full name) from the same confusion. Each failure ends the agent's turn.

Steps to reproduce
  1. Expose a service with a long package and class name and methods of varying length (anything that crosses the 64-character cutoff at different parts).
  2. Run a task in Agent Demo that needs one of the longer-named functions.
  3. The model calls a prefixed variant and the agent reports Called unknown function.
Suggested fix

Any of these would help:

  • Give all tools of one service the same prefix, e.g. pick the cutoff once per service (the deepest part every method of that service fits), or use ClassName_method with a short hash when even that exceeds 64 characters.
  • Resolve calls tolerantly: when the exact name is unknown, fall back to the unique tool whose name ends with the called name's ClassName_method suffix. A local patch doing this in GeminiProviderImpl removed the errors in our testing.
Environment
  • Testing Agent at a3a2a89 (main, Oct 23, 2026)
  • androidx.appfunctions 1.0.0-beta01
  • Android 17 (API 37) emulator, model gemini-3.5-flash

Related: #62, #63.

Dominant language
Kotlin
Stars
210
Forks
45
Avg merge
12h 24m
Merged PRs (30d)
3

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