To implement a Python function using OpenRouter’s API to send content to an AI model, receive results, and track the costs, you can follow this approach:

1. **API Request for Chat Completion**:
   - You’ll need to send a `POST` request to `https://openrouter.ai/api/v1/chat/completions`, including the model identifier, your message content, and your API key in the headers.
   - The request body should include the AI model you want to use (e.g., `"openai/gpt-3.5-turbo"`) and the `messages` array.

2. **Tracking Costs**:
   - The response will contain `usage` data, which includes `prompt_tokens`, `completion_tokens`, and `total_tokens`. This data allows you to calculate the cost based on token usage directly from the response.
   - Alternatively, to get detailed cost data, OpenRouter provides the `/api/v1/generation` endpoint. You can use the `id` from your initial response to query for specific stats, such as exact token counts and the calculated cost.

3. **Checking Account Balance**:
   - Currently, OpenRouter doesn’t appear to provide a direct API endpoint for account balance checks within their documented API endpoints, so this may need to be monitored from their platform dashboard directly.

Here’s a basic Python function demonstrating the API call, token tracking, and cost retrieval:

```python
import requests

def query_openrouter(content, model="openai/gpt-3.5-turbo"):
    url = "https://openrouter.ai/api/v1/chat/completions"
    headers = {
        "Authorization": "Bearer YOUR_API_KEY",
        "Content-Type": "application/json"
    }
    data = {
        "model": model,
        "messages": [{"role": "user", "content": content}]
    }

    response = requests.post(url, headers=headers, json=data)
    result = response.json()

    if "usage" in result:
        usage_data = result["usage"]
        cost_query_url = f"https://openrouter.ai/api/v1/generation?id={result['id']}"
        cost_response = requests.get(cost_query_url, headers=headers)
        cost_data = cost_response.json()
        
        return {
            "reply": result["choices"][0]["message"]["content"],
            "prompt_tokens": usage_data["prompt_tokens"],
            "completion_tokens": usage_data["completion_tokens"],
            "total_cost": cost_data["data"]["total_cost"]
        }
    else:
        return {"error": "No usage data available in the response"}

# Example usage
result = query_openrouter("What is the meaning of life?")
print(result)
```

For further details, OpenRouter’s official documentation outlines more on usage and token tracking options.