Gemini 2.5 flash 05-20 refusing to use certain tool calls

Gemini API
1

I have a payload that works fine on all Gemini APIs (2.5 pro exp, 2.0 flash, etc) but for some reason is not working in under 2.5 flash 05-20

{
  "generationConfig": {},
  "contents": [
    {
      "role": "user",
      "parts": [
        {
          "text": "sam: make a simple hello world artifact"
        }
      ]
    }
  ],
  "systemInstruction": {
    "role": "system",
    "parts": [
      {
        "text": "You are a helpful bot"
      }
    ]
  },
  "tools": [
    {
      "function_declarations": [
        {
          "name": "create_artifact",
          "description": "Creates a web artifact based on a specification",
          "parameters": {
            "type": "object",
            "properties": {
              "name": {
                "type": "string",
                "description": "A name for the artifact"
              },
              "specification": {
                "type": "string",
                "description": "specifications"
              }
            },
            "required": []
          }
        }
      ]
    }
  ]
}

When i call it it simply returns:

data: {"promptFeedback": {"blockReason": "OTHER"},"usageMetadata": {"promptTokenCount": 78,"totalTokenCount": 78,"promptTokensDetails": [{"modality": "TEXT","tokenCount": 78}]},"modelVersion": "models/gemini-2.5-flash-preview-05-20"}

I tested with a simple ā€œechoā€ tool call and it works, but this rather simple one fails.

Any ideas why this would be blocked on blockReason OTHER? Is a the latest Flash 2.5 being over protective.

3

I am facing the same issue with a simple get current day and get weather example tool:

class GetCurrentWeather(BaseM):
        """
        Gets the current weather
        """

        location: str = Field(..., description="The location of the weather")
        unit: str = Field(..., description="The unit of the temperature")

    class GetCurrentDay(BaseM):
        """
        Gets the current day
        """

        location: str = Field(..., description="The location of the day")

Without any tools it works. The same code works for gemini-2.5-flash-preview-04-17.

1 Like
5

Hi,

Thank you for bringing this to our attention, really appreciate flagging it. I have tested it on my end and confirmed that there is an issue with function calling in the newly updated gemini-2.5-flash-preview-05-20 model. I will escalated this issue to our product engineering team for a thorough investigation and resolution.

6 Likes
7

Hi @GUNAND_MAYANGLAMBAM ,
When can we expect feedback on this?
Thanks in advance

9

is this issue still exist? because i use 2.5 flash thinking if i use tools the same thing will happen too

11

I can confirm Iā€™m having the same issue with gemini-2.5-flash-preview-native-audio-dialog. Itā€™s calling functions inconsistently.

12

This is very consistent where it will attempt to just end the conversation with a missing reason when thinking is involved. Otherwise, when thinking is disabled, tool calling works better.

13

image
image1834Ɨ864 61.5 KB

Are there any more updates?
Iā€™m just using the built-in example tools and still canā€™t, and it says ā€˜Content Not Permittedā€™.
Even though the prompt wasnā€™t much, I was just asking how things are :3

16

Still facing this issue

18

Hi @Usama_Jalal , the issue has been fixed. What error were you getting?

Could you share the sample code or something similar?

Thanks

20

Happens to me as well with the new flash 2.5, requests structure and content similar to what Iā€™ve been running in last few months, suddenly getting non stop empty responses and block reason ā€œOtherā€

21

@GUNAND_MAYANGLAMBAM Any updates? this got worse over the last two days, almost every request I make either returns an empty structure or doesnā€™t follow my instructions at all.

22

Hey @Yovel_Cohen , Could you please share the sample code to reproduce the issue?

Thanks.

23

@GUNAND_MAYANGLAMBAM It doesnā€™t matter how I structure my requests, it seems like a request complexity issue, and just to mention the previous release of gemini 2.5 pro had the same issue.
once the prompt interleaves a lot of text, images and requests a structured output, the model seems to just ā€œgive upā€ and now I see the same with gemini 2.5 flash, on requests and data where it returned responses before the update.