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
| Attribute | Type | Description |
|---|---|---|
input.value |
String | Input to the operation (prompt, query, document) |
output.value |
String | Output from the operation (response, result, answer) |
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:
| Span Kind | Purpose | Common Use Case |
|---|---|---|
LLM |
Language model inference | OpenAI, Anthropic, local LLM calls |
EMBEDDING |
Vector generation | Text-to-vector conversion |
CHAIN |
Application flow orchestration | LangChain chains, custom workflows |
RETRIEVER |
Document/context retrieval | Vector DB queries, semantic search |
RERANKER |
Result reordering | Rerank retrieved documents |
TOOL |
External tool invocation | API calls, function execution |
AGENT |
Autonomous reasoning | ReAct agents, planning loops |
GUARDRAIL |
Safety/policy checks | Content moderation, PII detection |
EVALUATOR |
Quality assessment | Answer relevance, faithfulness scoring |