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

# Add Columns

> Add new columns to an experiment dataset

## Overview

Add new columns to an existing experiment dataset structure.

## Method Signature

```python theme={"system"}
# Synchronous
client.experiments.add_columns(
    experiment_id: str,
    columns: List[Dict[str, Any]]
) -> Dict[str, Any]

# Asynchronous
await client.experiments.add_columns(
    experiment_id: str,
    columns: List[Dict[str, Any]]
) -> Dict[str, Any]
```

## Parameters

<ParamField path="experiment_id" type="string" required>
  The unique identifier of the experiment
</ParamField>

<ParamField path="columns" type="List[Dict[str, Any]]" required>
  List of column definitions to add to the experiment
</ParamField>

## Returns

Returns a dictionary containing the updated experiment information.

## Example

```python theme={"system"}
from keywordsai import KeywordsAI

client = KeywordsAI(api_key="your-api-key")

# Add new columns to experiment
columns = [
    {
        "name": "confidence_score",
        "type": "float",
        "description": "Model confidence level"
    },
    {
        "name": "category",
        "type": "string",
        "description": "Response category"
    }
]

result = client.experiments.add_columns(
    experiment_id="exp_123",
    columns=columns
)

print(f"Added {len(columns)} columns to experiment")
```

## Error Handling

```python theme={"system"}
try:
    result = client.experiments.add_columns(
        experiment_id="exp_123",
        columns=columns
    )
except Exception as e:
    print(f"Error adding columns: {e}")
```