fix: support ComponentTool deserialization in OpenAI and Azure responses chat generators

[rautaditya2606]

Related Issues

Closes #12484

Proposed Changes

• Updated OpenAIResponsesChatGenerator.from_dict() and AzureOpenAIResponsesChatGenerator.from_dict() to correctly detect serialized Haystack tools using the {"type": ..., "data": ...} serialization envelope instead of matching only "haystack.tools.tool.Tool".
• Added support for deserializing ComponentTool instances while preserving raw OpenAI tool definitions.
• Added unit tests covering both serialized Haystack tools and raw OpenAI tools.
• Added a release note describing the fix.

Root Cause

from_dict() previously determined whether a tool required deserialization using:

tools[0].get("type") == "haystack.tools.tool.Tool"

This fails for ComponentTool, whose serialized representation uses:

{
    "type": "haystack.tools.component_tool.ComponentTool",
    "data": {...}
}

As a result, the serialized dictionary remained in tools instead of being deserialized.

When run() was subsequently called, _prepare_api_call() interpreted the dictionary as a raw OpenAI tool definition and passed the Haystack serialization structure to the OpenAI API, resulting in a 400 Bad Request.

Fix

The implementation now identifies serialized Haystack tools based on the presence of the "data" serialization envelope.

This allows ComponentTool and other serialized Haystack tools to be deserialized correctly while continuing to support raw OpenAI tool definitions such as:

{
    "type": "function",
    ...
}

Reproducer

from haystack.components.builders import PromptBuilder
from haystack.components.generators.chat.openai_responses import OpenAIResponsesChatGenerator
from haystack.tools import ComponentTool

tool = ComponentTool(
    name="prompt",
    description="Builds prompt",
    component=PromptBuilder(template="hi"),
)

generator = OpenAIResponsesChatGenerator(tools=[tool])
data = generator.to_dict()

restored = OpenAIResponsesChatGenerator.from_dict(data)

assert isinstance(restored.tools[0], ComponentTool)

Before the fix:

restored.tools[0] -> dict

After the fix:

restored.tools[0] -> ComponentTool

Tests

Ran the affected test suites:

hatch -e test run pytest \
  test/components/generators/chat/test_openai_responses.py \
  test/components/generators/chat/test_azure_responses.py

Result:

63 passed, 23 skipped in 1.42s

Also ran the newly added tests specifically:

hatch -e test run pytest \
  test/components/generators/chat/test_openai_responses.py \
  test/components/generators/chat/test_azure_responses.py \
  -k "test_from_dict_with_component_tool or test_from_dict_with_raw_openai_tools"

Result:

4 passed, 82 deselected in 0.34s

Checklist

• Read contributors guidelines and code of conduct
• Added/updated related issue reference
• Added unit tests
• Updated docstrings/documentation where required
• Added release note
• Used conventional commit type in PR title
• Ran pre-commit hooks and fixed reported issues

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Coverage report

Click to see where and how coverage changed

File	Statements	Missing	Coverage	Coverage (new stmts)	Lines missing
haystack/components/generators/chat
azure_responses.py
openai_responses.py
Project Total

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