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

# Introduction

> Track LLM costs, token usage, and latency with one line of code

## What is Costrace?

Costrace is an LLM observability SDK that automatically tracks cost, token usage, and latency for every API call you make to OpenAI, Anthropic, or Google Gemini.

No code changes required, just call `init()` and use your LLM SDKs as normal.

## Key Features

<CardGroup cols={2}>
  <Card title="Zero Configuration" icon="bolt">
    One line to initialize. Works by monkey-patching your existing LLM client
    libraries.
  </Card>

  <Card title="Real-time Cost Tracking" icon="dollar-sign">
    See exactly how much each API call costs, broken down by model and provider.
  </Card>

  <Card title="Latency Monitoring" icon="gauge">
    Track response times to identify slow endpoints and optimize performance.
  </Card>

  <Card title="Multi-Provider Support" icon="globe">
    OpenAI, Anthropic, and Gemini all tracked automatically.
  </Card>
</CardGroup>

## How It Works

Costrace works by patching the client libraries for OpenAI, Anthropic, and Gemini. When you make an API call, Costrace:

1. Records the start time
2. Lets your call proceed normally
3. Captures token usage and response time
4. Calculates the cost based on current pricing
5. Sends a trace to the Costrace backend (fire-and-forget, non-blocking)

All of this happens transparently! Your code doesn't change.

## Supported Providers

<AccordionGroup>
  <Accordion title="OpenAI">
    All
  </Accordion>

  <Accordion title="Anthropic">All</Accordion>

  <Accordion title="Google Gemini">
    All
  </Accordion>
</AccordionGroup>

## Next Steps

<CardGroup cols={2}>
  <Card title="Quick Start" icon="rocket" href="/quickstart">
    Get up and running in 2 minutes
  </Card>

  <Card title="Python SDK" icon="python" href="/sdks/python">
    Installation and usage for Python
  </Card>

  <Card title="Node.js SDK" icon="node-js" href="/sdks/nodejs">
    Installation and usage for Node.js
  </Card>

  <Card title="API Reference" icon="code" href="/api/traces">
    REST API documentation
  </Card>
</CardGroup>