awesome-copilot/plugins/phoenix/skills/phoenix-tracing/references/fundamentals-universal-attributes.md

Universal Attributes

This document covers attributes that can be used on any span kind in OpenInference.

Overview

These attributes can be used on any span kind to provide additional context, tracking, and metadata.

Input/Output

Attribute	Type	Description
input.value	String	Input to the operation (prompt, query, document)
input.mime_type	String	MIME type (e.g., "text/plain", "application/json")
output.value	String	Output from the operation (response, vector, result)
output.mime_type	String	MIME type of output

Why Capture I/O?

Always capture input/output for evaluation-ready spans:

• Phoenix evaluators (faithfulness, relevance, Q&A correctness) require input.value and output.value
• Phoenix UI displays I/O prominently in trace views for debugging
• Enables exporting I/O for creating fine-tuning datasets
• Provides complete context for analyzing agent behavior

Example attributes:

{
  "openinference.span.kind": "CHAIN",
  "input.value": "What is the weather?",
  "input.mime_type": "text/plain",
  "output.value": "I don't have access to weather data.",
  "output.mime_type": "text/plain"
}

See language-specific implementation:

• TypeScript: instrumentation-manual-typescript.md
• Python: instrumentation-manual-python.md

Session and User Tracking

Attribute	Type	Description
session.id	String	Session identifier for grouping related traces
user.id	String	User identifier for per-user analysis

Example:

{
  "openinference.span.kind": "LLM",
  "session.id": "session_abc123",
  "user.id": "user_xyz789"
}

Metadata

Attribute	Type	Description
metadata	string	JSON-serialized object of key-value pairs

Example:

{
  "openinference.span.kind": "LLM",
  "metadata": "{\"environment\": \"production\", \"model_version\": \"v2.1\", \"cost_center\": \"engineering\"}"
}