Mastra Tracing

Instrument agent applications built with Mastra

Mastra is an agentic framework that simplifies building complex AI applications with multi-agent workflows, tool integrations, and memory management.

Launch Phoenix

Phoenix Cloud

1. Sign up for an Arize Phoenix account at https://app.phoenix.arize.com/login

2. Grab your API key from the Keys option on the left bar.

3. In your code, configure environment variables for your endpoint and API key:

# .env, or shell environment

# And Collector Endpoint for Phoenix Cloud
PHOENIX_ENDPOINT="ADD YOUR PHOENIX ENDPOINT e.g. https://app.phoenix.arize.com/s/<example>/v1/traces"
# Add Phoenix API Key for tracing
PHOENIX_API_KEY="ADD YOUR PHOENIX API KEY"

Self-Hosted Phoenix

Install

npm install @mastra/arize

Configure Environment

Create a .env file that points Mastra to your Phoenix instance:

PHOENIX_ENDPOINT=http://localhost:6006/v1/traces
PHOENIX_API_KEY=your-api-key # Optional for local Phoenix
PHOENIX_PROJECT_NAME=mastra-service # Optional, defaults to "mastra-service"

Setup

Initialize the Arize AX exporter inside your Mastra project:

import { Mastra } from "@mastra/core";
import { ArizeExporter } from "@mastra/arize";

export const mastra = new Mastra({
  // ... other config (agents, workflows, etc.)
  observability: {
    configs: {
      arize: {
        serviceName: process.env.PHOENIX_PROJECT_NAME || "mastra-service",
        exporters: [
          new ArizeExporter({
            endpoint: process.env.PHOENIX_ENDPOINT!,
            apiKey: process.env.PHOENIX_API_KEY,
            projectName: process.env.PHOENIX_PROJECT_NAME,
          }),
        ],
      },
    },
  },
});

Create Agents and Tools

From here you can use Mastra as normal. Create agents with tools and run them:

import { openai } from "@ai-sdk/openai";
import { Agent } from "@mastra/core/agent";
import { Mastra } from "@mastra/core";
import { ArizeExporter } from "@mastra/arize";
import { z } from "zod";

// Create a simple weather tool
const weatherTool = {
  name: "weatherTool",
  description: "Get current weather for a location",
  parameters: z.object({
    location: z.string().describe("The city and country"),
  }),
  execute: async ({ location }) => {
    // Simulate weather API call
    return {
      location,
      temperature: "22°C",
      condition: "Sunny",
      humidity: "60%",
    };
  },
};

// Create an agent
const weatherAgent = new Agent({
  name: "Weather Assistant",
  instructions: "You help users get weather information. Use the weather tool to get current conditions.",
  model: openai("gpt-4o-mini"),
  tools: { weatherTool },
});

// Register the agent with Mastra instance
const mastra = new Mastra({
  agents: { weatherAgent },
  observability: {
    configs: {
      arize: {
        serviceName: process.env.PHOENIX_PROJECT_NAME || "mastra-service",
        exporters: [
          new ArizeExporter({
            endpoint: process.env.PHOENIX_ENDPOINT!,
            apiKey: process.env.PHOENIX_API_KEY,
            projectName: process.env.PHOENIX_PROJECT_NAME,
          }),
        ],
      },
    },
  },
});

Running Your Application

To test your application with Phoenix tracing:

# Start the Mastra dev server
mastra dev

## or, build and run the production server with instrumentation enabled
# npm run build
# node --import=./.mastra/output/instrumentation.mjs .mastra/output/index.mjs

This will:

1. Initialize the tracing SDK with your observability configuration

2. Start the Mastra playground at http://localhost:4111

3. Enable trace export to Phoenix at http://localhost:6006

Interact with your agents:

• Via Playground: Navigate to http://localhost:4111/playground to chat with agents

• Via API: Make requests to the generated API endpoints

• Programmatically: Create test scripts that run within the Mastra dev environment

Observe

Now that you have tracing setup, all agent runs, tool calls, and model interactions will be streamed to your running Phoenix for observability and evaluation.

Resources

• Working example

• Mastra CLI Documentation