Required and Recommended Attributes

This document covers the required attribute and highly recommended attributes for all OpenInference spans.

Required Attribute

Every span MUST have exactly one required attribute:

{
  "openinference.span.kind": "LLM"
}

Highly Recommended Attributes

While not strictly required, these attributes are highly recommended on all spans as they:

• Enable evaluation and quality assessment
• Help understand information flow through your application
• Make traces more useful for debugging

Input/Output Values

Example:

{
  "openinference.span.kind": "LLM",
  "input.value": "What is the capital of France?",
  "output.value": "The capital of France is Paris."
}

Why these matter:

• Evaluations: Many evaluators (faithfulness, relevance, hallucination detection) require both input and output to assess quality
• Information flow: Seeing inputs/outputs makes it easy to trace how data transforms through your application
• Debugging: When something goes wrong, having the actual input/output makes root cause analysis much faster
• Analytics: Enables pattern analysis across similar inputs or outputs

Phoenix Behavior:

• Input/output displayed prominently in span details
• Evaluators can automatically access these values
• Search/filter traces by input or output content
• Export inputs/outputs for fine-tuning datasets

Valid Span Kinds

There are exactly 9 valid span kinds in OpenInference: