OpenAPIConnector

OpenAPIConnector is a component that acts as an interface between the Haystack ecosystem and OpenAPI services.

Consider using MCP instead

These OpenAPI components are a legacy way to connect Haystack to external APIs. For most use cases, we recommend the MCPTool instead: it is the modern, standardized way to give your pipelines and agents access to external tools and services.

Most common position in a pipeline	Anywhere, after components providing input for its run parameters
Mandatory init variables	openapi_spec: The OpenAPI specification for the service. Can be a URL, file path, or raw string.
Mandatory run variables	operation_id: The operationId from the OpenAPI spec to invoke.
Output variables	response: A REST service response
API reference	OpenAPI
GitHub link	https://github.com/deepset-ai/haystack-core-integrations/tree/main/integrations/openapi
Package name	openapi-haystack

Overview

The OpenAPIConnector is a component within the Haystack ecosystem that allows direct invocation of REST endpoints defined in an OpenAPI (formerly Swagger) specification. It acts as a bridge between Haystack pipelines and any REST API that follows the OpenAPI standard, enabling dynamic method calls, authentication, and parameter handling.

To use the OpenAPIConnector, ensure that you have the openapi-haystack package installed:

shell

pip install openapi-haystack

Unlike OpenAPIServiceConnector, which works with LLMs, OpenAPIConnector directly calls REST endpoints using explicit input arguments.

Usage

On its own

You can initialize and use the OpenAPIConnector on its own by passing an OpenAPI specification and other parameters:

python

from haystack.utils import Secret
from haystack_integrations.components.connectors.openapi import OpenAPIConnector

connector = OpenAPIConnector(
    openapi_spec="https://bit.ly/serperdev_openapi",
    credentials=Secret.from_env_var("SERPERDEV_API_KEY"),
    service_kwargs={"config_factory": my_custom_config_factory},
)

response = connector.run(
    operation_id="search",
    arguments={"q": "Who was Nikola Tesla?"},
)

Output

The OpenAPIConnector returns a dictionary containing the service response:

json

{
    "response": { // here goes REST endpoint response JSON
    }
}

In a pipeline

The OpenAPIConnector can be integrated into a Haystack pipeline to interact with OpenAPI services. For example, here’s how you can link the OpenAPIConnector to a pipeline:

python

from haystack import Pipeline
from haystack_integrations.components.connectors.openapi import OpenAPIConnector
from haystack.dataclasses.chat_message import ChatMessage
from haystack.utils import Secret

# Initialize the OpenAPIConnector
connector = OpenAPIConnector(
    openapi_spec="https://bit.ly/serperdev_openapi",
    credentials=Secret.from_env_var("SERPERDEV_API_KEY"),
)

# Create a ChatMessage from the user
user_message = ChatMessage.from_user(text="Who was Nikola Tesla?")

# Define the pipeline
pipeline = Pipeline()
pipeline.add_component("openapi_connector", connector)

# Run the pipeline
response = pipeline.run(
    data={
        "openapi_connector": {
            "operation_id": "search",
            "arguments": {"q": user_message.text},
        },
    },
)

# Extract the answer from the response
answer = response.get("openapi_connector", {}).get("response", {})
print(answer)