---
title: "OpenAPIServiceConnector"
id: openapiserviceconnector
slug: "/openapiserviceconnector"
description: "`OpenAPIServiceConnector` is a component that acts as an interface between the Haystack ecosystem and OpenAPI services."
---

# OpenAPIServiceConnector

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

<div className="key-value-table">

|  |  |
| --- | --- |
| **Most common position in a pipeline** | Flexible |
| **Mandatory run variables** | `messages`: A list of [`ChatMessage`](../../concepts/data-classes/chatmessage.mdx)  objects where the last message is expected to carry parameter invocation payload.  <br /> <br />`service_openapi_spec`: OpenAPI specification of the service being invoked. It can be YAML/JSON, and all ref values must be resolved.  <br /> <br />`service_credentials`: Authentication credentials for the service. We currently support two OpenAPI spec v3 security schemes:  <br /> <br />1. http – for Basic, Bearer, and other HTTP authentication schemes;   2. apiKey – for API keys and cookie authentication. |
| **Output variables** | `service_response`: A dictionary that is a list of [`ChatMessage`](../../concepts/data-classes/chatmessage.mdx)  objects where each message corresponds to a function invocation.   If a user specifies multiple function calling requests, there will be multiple responses. |
| **API reference** | [Connectors](/reference/connectors-api) |
| **GitHub link** | https://github.com/deepset-ai/haystack/blob/main/haystack/components/connectors/openapi_service.py |

</div>

## Overview

`OpenAPIServiceConnector` acts as a bridge between Haystack ecosystem and OpenAPI services. This component works by using information from a `ChatMessage` to dynamically invoke service methods. It handles parameter payload parsing from `ChatMessage`, service authentication, method invocation, and response formatting, making it easier to integrate OpenAPI services.

To use `OpenAPIServiceConnector`, you need to install the optional `openapi3` dependency with:

```shell
pip install openapi3
```

`OpenAPIServiceConnector` component doesn’t have any init parameters.

## Usage

### On its own

This component is primarily meant to be used in pipelines, as [`OpenAPIServiceToFunctions`](../converters/openapiservicetofunctions.mdx), in tandem with the function calling model, resolves the actual function calling parameters that are injected as invocation parameters for `OpenAPIServiceConnector`.

### In a pipeline

Let's say we're linking the Serper search engine to a pipeline. Here, `OpenAPIServiceConnector` uses the abilities of `OpenAPIServiceToFunctions`. `OpenAPIServiceToFunctions` first fetches and changes the [Serper's OpenAPI specification](https://bit.ly/serper_dev_spec) into a format that OpenAI's function calling mechanism can understand. Then, `OpenAPIServiceConnector` activates the Serper service using this specification.

More precisely, `OpenAPIServiceConnector` dynamically calls methods defined in the Serper OpenAPI specification. This involves reading chat messages or other inputs to extract function call parameters, handling authentication with the Serper service, and making the right API calls. The connector makes sure that the method call follows the Serper API requirements, such as correct formatting requests and handling responses.

Note that we used Serper just as an example here. This could be any OpenAPI-compliant service.

:::note
To run the following code snippet, note that you have to have your own Serper and OpenAI API keys.

:::

```python
import json
import requests

from typing import Dict, Any, List
from haystack import Pipeline
from haystack.components.generators.utils import print_streaming_chunk
from haystack.components.converters import OpenAPIServiceToFunctions, OutputAdapter
from haystack.components.generators.chat import OpenAIChatGenerator
from haystack.components.connectors import OpenAPIServiceConnector
from haystack.components.fetchers import LinkContentFetcher
from haystack.dataclasses import ChatMessage, ByteStream
from haystack.utils import Secret


def prepare_fc_params(openai_functions_schema: Dict[str, Any]) -> Dict[str, Any]:
    return {
        "tools": [{"type": "function", "function": openai_functions_schema}],
        "tool_choice": {
            "type": "function",
            "function": {"name": openai_functions_schema["name"]},
        },
    }


system_prompt = requests.get("https://bit.ly/serper_dev_system_prompt").text
serper_spec = requests.get("https://bit.ly/serper_dev_spec").text

pipe = Pipeline()
pipe.add_component("spec_to_functions", OpenAPIServiceToFunctions())
pipe.add_component(
    "functions_llm",
    OpenAIChatGenerator(
        api_key=Secret.from_token(llm_api_key),
        model="gpt-3.5-turbo-0613",
    ),
)
pipe.add_component("openapi_container", OpenAPIServiceConnector())
pipe.add_component(
    "a1",
    OutputAdapter(
        "{{functions[0] | prepare_fc}}",
        Dict[str, Any],
        {"prepare_fc": prepare_fc_params},
    ),
)
pipe.add_component("a2", OutputAdapter("{{specs[0]}}", Dict[str, Any]))
pipe.add_component(
    "a3",
    OutputAdapter("{{system_message + service_response}}", List[ChatMessage]),
)
pipe.add_component(
    "llm",
    OpenAIChatGenerator(
        api_key=Secret.from_token(llm_api_key),
        model="gpt-4-1106-preview",
        streaming_callback=print_streaming_chunk,
    ),
)

pipe.connect("spec_to_functions.functions", "a1.functions")
pipe.connect("spec_to_functions.openapi_specs", "a2.specs")
pipe.connect("a1", "functions_llm.generation_kwargs")
pipe.connect("functions_llm.replies", "openapi_container.messages")
pipe.connect("a2", "openapi_container.service_openapi_spec")
pipe.connect("openapi_container.service_response", "a3.service_response")
pipe.connect("a3", "llm.messages")

user_prompt = "Why was Sam Altman ousted from OpenAI?"

result = pipe.run(
    data={
        "functions_llm": {
            "messages": [
                ChatMessage.from_system("Only do function calling"),
                ChatMessage.from_user(user_prompt),
            ],
        },
        "openapi_container": {"service_credentials": serper_dev_key},
        "spec_to_functions": {"sources": [ByteStream.from_string(serper_spec)]},
        "a3": {"system_message": [ChatMessage.from_system(system_prompt)]},
    },
)
```
