> ## Documentation Index
> Fetch the complete documentation index at: https://docs.upsonic.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Start Agent API

> Configure inputs, outputs, and run your agent as a FastAPI server

## Overview

The Agent API automatically generates a FastAPI server from your `upsonic_config.json` configuration. The server exposes a `/call` endpoint that accepts inputs defined in your input schema and returns outputs matching your output schema.

The API supports both `application/json` and `multipart/form-data` content types, making it compatible with web forms, file uploads, and JSON-based clients.

## Configure Inputs

Inputs are defined in the `input_schema` section of `upsonic_config.json`:

```json theme={null}
{
    "input_schema": {
        "inputs": {
            "question": {
                "type": "string",
                "description": "The question of the User",
                "required": True,
                "default": None
            }
        }
    }
}
```

Supported input types include:

* `string`: Text input
* `number`: Numeric values
* `integer`: Whole numbers
* `boolean`: True/false values
* `array` or `list`: Arrays of values
* `json` or `object`: JSON objects
* `file` or `binary`: File uploads

Set `required: true` for mandatory inputs and provide `default` values for optional fields.

## Configure Outputs

Outputs are defined in the `output_schema` section:

```json theme={null}
{
    "output_schema": {
        "answer": {
            "type": "string",
            "description": "Answer of the agent"
        }
    }
}
```

Your agent's `main()` function should return a dictionary matching the output schema structure. The API automatically validates and formats the response according to these definitions.

## Run FastAPI of your Agent

Start the FastAPI server with:

```bash theme={null}
upsonic run
```

The server starts on `http://localhost:8000` by default. Customize the host and port:

```bash theme={null}
upsonic run --host 0.0.0.0 --port 8080
```

Once running, you can:

* Access interactive API docs at `http://localhost:8000/docs`
* Test the `/call` endpoint directly from the Swagger UI
* Send HTTP requests to `POST http://localhost:8000/call`

The API automatically generates OpenAPI schemas from your input/output configurations, enabling full type validation and interactive testing through the documentation interface.