[BUG] output_json not working with custom_openai

[WoBuGs]

Description

I have a setup with Ollama and Open-WebUI. Agents do some tasks, and then output a json file.

I ensure that the output is valid by using the output_json parameter in my task definition:

    @task
    def my_task(self) -> Task:
        return Task(
            config=self.tasks_config['my_task'],
            tools=[],
            output_file="outputs/task_output.json",
            output_json=TaskOutput
        )

So far I used Ollama as model provider in my crews. Now I want to move everything to the OpenAI-compatible API from Open-WebUI, to handle users, API keys, etc.

For testing, I have the following two ini files:

MODEL=ollama/granite3.2:8b
BASE_URL=http://<ollama url>:11434

and

OPENAI_MODEL_NAME=custom_openai/granite3.2:8b
OPENAI_API_BASE=https://<openwebui url>/ollama/v1
OPENAI_API_KEY=<API key>

The crew runs for both, BUT for the second one, I get the following error at the end of the exection:

 Failed to convert text into JSON, error: Instructor does not support multiple tool calls, use List[Model] instead. Using raw output instead.

The outputed JSON file is not valid, and this last steps hangs for a few minutes.

Steps to Reproduce

1. Set up a task with the output_json parameter.
2. Run the task using ollama as backend.
3. Run the task using openwebui (OpenAI-compatible API) as backend.

Expected behavior

Valid JSON and not error.

Screenshots/Code snippets

See description.

Operating System

Ubuntu 24.04

Python Version

3.12

crewAI Version

0.102.0

crewAI Tools Version

0.36.0

Virtual Environment

Venv

Evidence

See description.

Possible Solution

None

Additional context

None

[Vidit-Ostwal]

I am not sure on this.
I think the issue is LiteLLM which is called internally.
Found this on reddit : https://www.reddit.com/r/selfhosted/comments/1iof274/anyone_here_running_openwebui_and_litellm/

[prdai]

Hey there,

This GitHub comment might provide relevant insights and potential workarounds:
567-labs/instructor#1111 (comment)

[github-actions]

This issue is stale because it has been open for 30 days with no activity. Remove stale label or comment or this will be closed in 5 days.

[lucasgomide]

@WoBuGs can you share your tasks and agents config?

[github-actions]

This issue is stale because it has been open for 30 days with no activity. Remove stale label or comment or this will be closed in 5 days.

[WoBuGs]

Sorry for the delay. I don't have this configuration anymore :/

But ultimatly, I think the issue is/was more related to Open-WebUI and how it exposes an OpenAI compatible API.