Setup Install the Braintrust SDK and the Agent Framework integration, then set your API keys. The examples below use OpenAI. ```bash theme={"theme":{"light":"github-light","dark":"github-dark-dimmed"}} dotnet add package Braintrust.Sdk dotnet add package Braintrust.Sdk.AgentFramework dotnet add package Microsoft.Agents.AI.OpenAI ``` ```bash title=".env" theme={"theme":{"light":"github-light","dark":"github-dark-dimmed"}} BRAINTRUST_API_KEY= OPENAI_API_KEY= ``` Manual instrumentation To trace the Agent Framework, add Braintrust’s middleware to your chat client and wrap your agent. `UseBraintrustTracing` instruments both the LLM calls and the tool invocations on the `ChatClientBuilder`, and `WithBraintrustAgentTracing` wraps the agent so each run is captured as a span. ```csharp #skip-compile theme={"theme":{"light":"github-light","dark":"github-dark-dimmed"}} using Braintrust.Sdk; using Braintrust.Sdk.AgentFramework; using Microsoft.Agents.AI; using Microsoft.Extensions.AI; using OpenAI; var braintrust = Braintrust.Sdk.Braintrust.Get(); var activitySource = braintrust.GetActivitySource(); // Add Braintrust tracing to the chat client (LLM calls + function calls) var chatClient = new OpenAIClient(Environment.GetEnvironmentVariable("OPENAI_API_KEY")) .GetChatClient("gpt-5-mini").AsIChatClient() .AsBuilder() .UseBraintrustTracing(activitySource) .Build(); var getWeather = AIFunctionFactory.Create( (string city) => $"The weather in {city} is sunny, 72°F.", "GetWeather", "Gets the current weather for a city."); // Wrap the agent so each run is traced var agent = new ChatClientAgent( chatClient, instructions: "You are a helpful assistant. Use tools when appropriate.", name: "WeatherAgent", tools: [getWeather]) .WithBraintrustAgentTracing(activitySource); var session = await agent.CreateSessionAsync(); var response = await agent.RunAsync("What's the weather like in Seattle?", session); Console.WriteLine(response.Text); ``` `UseBraintrustTracing` combines `UseBraintrustLLMTracing` (LLM calls) and `UseBraintrustFunctionTracing` (tool calls). Call a single method instead to trace only that layer. Each method accepts a `captureMessageContent` flag, and function tracing accepts a `captureToolArguments` flag, to turn off capturing message or argument content. What Braintrust traces Braintrust captures a span at each level of the Agent Framework pipeline: * Agent run spans (`agent:`), with input and output messages, agent name and ID, token usage (prompt, completion, and total), and time to first token. * Chat completion spans (`Chat Completion` and `Chat Completion Stream`), with input and output messages, request and response model, and token usage (prompt, completion, and total). Streamed responses are aggregated and tagged with `stream`. * Function call spans (`function:`), with the function name, arguments, result, call iteration and index, and duration. * Errors on any span, including the exception message and details. Set `captureMessageContent: false` to omit message content, or `captureToolArguments: false` to omit function arguments and results. Resources * [Microsoft Agent Framework](https://github.com/microsoft/agent-framework) * [Braintrust C# SDK reference](/reference/sdks/csharp) * [Braintrust .NET SDK on GitHub](https://github.com/braintrustdata/braintrust-sdk-dotnet)