> ## Documentation Index > Fetch the complete documentation index at: https://docs.inceptionlabs.ai/llms.txt > Use this file to discover all available pages before exploring further. # Vapi > Build a low-latency voice agent in Vapi using Mercury 2. This tutorial creates a voice agent, integrating the realtime reasoning intelligence of Mercury 2 with Vapi. For this demo, you will need an **Inception** [API key](https://platform.inceptionlabs.ai/dashboard/api-keys) and a [Vapi account](https://vapi.ai). ## Authentication 1. Navigate to **Integrations** in the Vapi sidebar. Vapi sidebar with the Integrations section open 2. Under **Model Providers**, click into **Custom LLM** (bottom right). Custom LLM option under Model Providers in Vapi 3. Fill in your Inception API key and click **Save**. Entering the Inception API key in Vapi's Custom LLM provider ## Setting up your Mercury voice agent 1. Navigate to **Agents** in the Vapi sidebar and select **Create Assistant.** Creating a new assistant in Vapi 2. Name your assistant and select your desired assistant template. Naming the assistant and choosing a template in Vapi 3. Select **Custom LLM** from the Model dropdown: Selecting Custom LLM from the model dropdown in Vapi 4. Fill in model details as follows: * Set **Custom LLM URL** as `https://api.inceptionlabs.ai/v1` * Set **Model** as `mercury-2` * Set **Temperature** to `0.75` * Set **Max Tokens** to a slightly higher value, like `4096`. This is because the default reasoning effort is `medium`, and Max Tokens includes reasoning tokens. * Configure **First Message Mode**, **First Message** and **System Prompt** as desired. * Scroll down to manage **Tools**, **Structured Outputs** and more. Configuring the Custom LLM URL, model, temperature, and max tokens in Vapi 5. When you're ready, hit **Publish** in the top right corner, and **Talk** to speak to Mercury 2! Publishing the Vapi assistant and talking to Mercury 2