.NET: UseOpenTelemetry() does not emit ActivityEvents as specified in OpenTelemetry GenAI Semantic Conventions

[gijswalraven]

Summary

Microsoft Agent Framework's UseOpenTelemetry() (via Microsoft.Extensions.AI) implements span attributes from the OpenTelemetry GenAI Semantic Conventions, but does not emit the required ActivityEvents defined in the specification.

Current Behavior

When using MAF with OpenTelemetry:

var chatClient = azureClient
    .GetChatClient(deploymentName)
    .AsIChatClient()
    .AsBuilder()
    .UseOpenTelemetry(sourceName: "MyAgent", configure: c => c.EnableSensitiveData = true)
    .Build();

What's emitted:

• ✅ Activity spans with gen_ai.* attributes
• ✅ Histogram metrics (gen_ai.client.token.usage, gen_ai.client.operation.duration)
• ❌ Missing: gen_ai.client.inference.operation.details ActivityEvents

Expected Behavior

According to the OpenTelemetry GenAI Events specification, implementations should emit structured ActivityEvent objects with event name gen_ai.client.inference.operation.details.

Example of expected event structure:

var tags = new ActivityTagsCollection
{
    { "gen_ai.operation.name", "chat" },
    { "gen_ai.request.model", modelId },
    { "gen_ai.response.model", response.ModelId },
    { "gen_ai.usage.input_tokens", inputTokens },
    { "gen_ai.usage.output_tokens", outputTokens },
    { "gen_ai.output.messages", responseText } // Optional
};

var activityEvent = new ActivityEvent("gen_ai.client.inference.operation.details", tags: tags);
Activity.Current?.AddEvent(activityEvent);

Distinction: Events vs Span Attributes

• Span Attributes: Key-value pairs attached to spans for the entire operation duration
• ActivityEvents: Timestamped, structured occurrences within a span representing discrete points in time

Both are defined in the OpenTelemetry GenAI spec and serve different purposes in observability.

Impact

Without ActivityEvents:

1. Incomplete spec compliance - Missing a key observability signal defined in GenAI conventions
2. Limited analysis capabilities - Events enable time-series analysis of LLM operations
3. Reduced interoperability - Tools expecting full GenAI spec compliance won't receive event data

Proposal

Extend UseOpenTelemetry() (or add UseOpenTelemetryEvents()) to emit ActivityEvents as specified in the GenAI semantic conventions. This would provide:

• Full compliance with OpenTelemetry GenAI spec
• Unified observability without custom extensions
• Better time-series analysis of LLM operations
• Improved interoperability with GenAI observability tools

References

• OpenTelemetry GenAI Events Spec
• OpenTelemetry GenAI Semantic Conventions
• OpenTelemetryChatClient Source - Current implementation

Environment

• Microsoft Agent Framework: v1.0.0-preview.260128.1
• Microsoft.Extensions.AI: (bundled with MAF)
• Target Framework: .NET 8.0

[gijswalraven]

Additional Context: EnableSensitiveData

The current UseOpenTelemetry() implementation includes an EnableSensitiveData configuration option that captures input/output messages as span attributes:

.UseOpenTelemetry(
    sourceName: "MyAgent",
    configure: c => c.EnableSensitiveData = true)

This captures:

• gen_ai.input.messages - Input prompt content
• gen_ai.output.messages - Response content

Key distinction: This captures content as span attributes, not ActivityEvents. Both are valuable but serve different observability purposes:

• Span Attributes: Metadata for the entire operation span
• ActivityEvents: Timestamped, structured occurrences within the span

For full OpenTelemetry GenAI spec compliance, both mechanisms should be supported. The event-based approach (gen_ai.client.inference.operation.details) provides better time-series analysis and structured event logging capabilities.

The EnableSensitiveData functionality is excellent - it just needs to be complemented with ActivityEvent emission to fully comply with the GenAI semantic conventions.

[stephentoub]

does not emit the required ActivityEvents defined in the specification

Where do you see events listed as required in the convention? It explicitly states "GenAI instrumentations MAY capture user inputs sent to the model and responses received from it as events."

[gijswalraven]

does not emit the required ActivityEvents defined in the specification

Where do you see events listed as required in the convention? It explicitly states "GenAI instrumentations MAY capture user inputs sent to the model and responses received from it as events."

I did NOT mention this as REQUIRED. I mentioned that according to the protocol we MAY add this feature here. I am ok marking this as a feature request.