.NET Agent Performance Metrics and Token Usage

[lukemurraynz]

Current Behavior: No built-in telemetry for:

Total tokens consumed (input + output)
Cost estimation
Latency breakdown (network, processing, tool calls)
Success/failure rates
Problem: Production applications need to track:

Cost per conversation
Performance bottlenecks
Token usage trends for budgeting
Recommended Changes:

Add Metrics property to AgentRunResponse
Include token counts, latency, and cost estimates
Support custom metric providers
Integrate with OpenTelemetry
Example Desired API:

var result = await agent.RunAsync(prompt);

Console.WriteLine($"Tokens used: {result.Metrics.TotalTokens}");
Console.WriteLine($"  Input: {result.Metrics.InputTokens}");
Console.WriteLine($"  Output: {result.Metrics.OutputTokens}");
Console.WriteLine($"Estimated cost: ${result.Metrics.EstimatedCost:F4}");
Console.WriteLine($"Latency: {result.Metrics.TotalLatency}ms");
Console.WriteLine($"  LLM: {result.Metrics.LlmLatency}ms");
Console.WriteLine($"  Tools: {result.Metrics.ToolLatency}ms");

[stephentoub]

Total tokens consumed (input + output)

Input and output token counts are logged as part of telemetry, both at the agent level and at the IChatClient level.

Latency breakdown (network, processing, tool calls)

This is also logged as part of telemetry.

[lukemurraynz]

Thanks, Stephen!