> For the complete documentation index, see [llms.txt](https://docs.parasail.io/parasail-docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.parasail.io/parasail-docs/use-cases/agents-tool-calling.md).

# Agents and Tool Calling

Build AI agents that can call functions, reason across multiple steps, and interact with external tools. Parasail supports both the Chat Completions API with tool calling and the Responses API for multi-turn agentic workflows.

## Two approaches

| Approach                 | Best for                                      | API                    |
| ------------------------ | --------------------------------------------- | ---------------------- |
| Chat Completions + tools | Single-model function calling                 | `/v1/chat/completions` |
| Responses API            | Multi-turn agentic loops, parallel tool calls | `/v1/responses`        |

## Function calling with Chat Completions

```python
from openai import OpenAI
import json

client = OpenAI(
    base_url="https://api.parasail.io/v1",
    api_key="<PARASAIL_API_KEY>"
)

tools = [
    {
        "type": "function",
        "function": {
            "name": "get_weather",
            "description": "Get the current weather for a city.",
            "parameters": {
                "type": "object",
                "properties": {
                    "city": {"type": "string", "description": "City name"}
                },
                "required": ["city"]
            }
        }
    }
]

response = client.chat.completions.create(
    model="parasail-deepseek-r1",
    messages=[{"role": "user", "content": "What's the weather in Tokyo?"}],
    tools=tools
)

print(response.choices[0].message.tool_calls)
```

## Responses API (multi-turn agentic)

The Responses API supports multi-turn conversations with parallel tool calls. It uses the standard Parasail gateway:

* **Base URL**: `https://api.parasail.io/v1`
* **Required**: Set `store: false` on every request (server-side state is not supported).

```python
from openai import OpenAI

client = OpenAI(
    base_url="https://api.parasail.io/v1",
    api_key="<PARASAIL_API_KEY>"
)

response = client.responses.create(
    model="parasail-kimi-k25-elicit",
    store=False,
    tools=tools,
    input=[{"role": "user", "content": "What's the weather in Tokyo?"}]
)
```

## Relevant guides

* [Tool/Function Calling guide](/parasail-docs/guides/tool-function-calling.md)—detailed function calling tutorial

## API reference

* [Chat Completions API](/parasail-docs/api-reference/chat-completions.md)
* [Responses API](/parasail-docs/products/overview/responses-api.md)—full spec, compatibility table, and agentic loop example