Incompatibility of assistant with tool_calls and tool role in the /v1/responses endpoint

[fsrocha-filipe]

Confirm this is an issue with the Python library and not an underlying OpenAI API

• This is an issue with the Python library

Describe the bug

Context:

While migrating from the POST /v1/chat/completions endpoint to POST /v1/responses, I encountered issues with some previously valid payloads used by my agent system. After investigating, I found inconsistencies related to the usage of the assistant role with tool_calls, and the tool role itself.

In the older endpoint (/chat/completions), I’ve been successfully using a complex conversational flow where multiple roles are interleaved to allow autonomous interactions between the agent, tools, and users.

Working payload in /chat/completions

{
  "input": [
    {
      "role": "developer",
      "content": "prompt"
    },
    {
      "role": "user",
      "content": "..."
    },
    {
      "role": "assistant",
      "tool_calls": { ... }
    },
    {
      "role": "tool",
      "content": "...",
      "tool_call_id": "call_xxxx"
    },
    {
      "role": "developer",
      "content": "..."
    }
  ]
}

Issues encountered when using /v1/responses

Error with assistant + tool_calls:

{
  "error": {
    "message": "Unknown parameter: 'input[3].tool_calls'.",
    "type": "invalid_request_error",
    "param": "input[3].tool_calls",
    "code": "unknown_parameter"
  }
}

Error with tool role:

{
  "error": {
    "message": "Invalid value: 'tool'. Supported values are: 'assistant', 'system', 'developer', and 'user'.",
    "type": "invalid_request_error",
    "param": "input[3]",
    "code": "invalid_value"
  }
}

Questions

The official OpenAI documentation does not yet provide detailed guidance on the differences in role support between the two endpoints especially around tool interactions.

Therefore, I’d like to clarify:

1. Does the /v1/responses endpoint support messages with role: assistant containing tool_calls?
2. Has the tool role been deprecated in the new API, or is there an alternative way to represent tool responses?
3. Is there any migration documentation that specifically covers how to adapt this kind of tool-augmented, multi-turn agent flow?

This tool-based multi-role setup is critical for more advanced agents capable of autonomous reasoning and external action execution. If /responses no longer supports these structures, it significantly limits the usability of autonomous agents with tools.

Sincerely,
Filipe Rocha

To Reproduce

The error consistently occurs both when using the OpenAI SDK and when sending raw requests via cURL, which suggests it's not a client-side issue.

curl --location 'https://api.openai.com/v1/responses' \
--header 'Authorization: Bearer xxxxxxxxx' \
--header 'Content-Type: application/json' \
--data '{
    "model": "gpt-4.1",
    "temperature": 0,
    "top_p": 1,
    "max_output_tokens": 2048,
    "input": [
        {
            "role": "developer",
            "content": "prompt"
        },
        {
            "role": "user",
            "content": "user demand"
        },
        {
            "role": "user",
            "content": "user demand"
        },
        {
            "role": "assistant",
            "content": [],
            "tool_calls": [
                {
                    "id": "call_hCvlhe2zU31tkId6iRbT23gC",
                    "type": "function",
                    "function": {
                        "arguments": "{}",
                        "name": "name"
                    }
                }
            ]
        },
        {
            "role": "tool",
            "content": "....",
            "tool_call_id": "call_hCvlhe2zU31tkId6iRbT23gC"
        },
        {
            "role": "assistant",
            "content": "..."
        },
        {
            "role": "assistant",
            "content": "..."
        },
        {
            "role": "developer",
            "content": "prompt"
        }
    ],
    "tools": [
        {
            "type": "function",
                "parameters": {
                    "properties": {
                         "monologo_interno_do_aborto": {
                            "description": "description",
                               "type": "string"
                         }
                    },
                    "required": [
                       "monologo_interno_do_aborto"
                    ],
                    "type": "object"
                },
                "name": "abortar_planejamento",
                "description": "description"
        }
    ]
}'

Code snippets

params = {
   **params.to_payload(),
   "model": model_config.model,
}
responses = await client.responses.create(**params)

OS

macOS

Python version

v3.9.6

Library version

v1.108.0

[ievgennaida]

Also stream_options={"include_usage": True} is not supported by the responses.