# CHAIN Spans
## Purpose
CHAIN spans represent orchestration layers in your application (LangChain chains, custom workflows, application entry points). Often used as root spans.
## Required Attributes
| Attribute | Type | Description | Required |
| ------------------------- | ------ | --------------- | -------- |
| `openinference.span.kind` | String | Must be "CHAIN" | Yes |
## Common Attributes
CHAIN spans typically use [Universal Attributes](fundamentals-universal-attributes.md):
- `input.value` - Input to the chain (user query, request payload)
- `output.value` - Output from the chain (final response)
- `input.mime_type` / `output.mime_type` - Format indicators
## Example: Root Chain
```json
{
"openinference.span.kind": "CHAIN",
"input.value": "{\"question\": \"What is the capital of France?\"}",
"input.mime_type": "application/json",
"output.value": "{\"answer\": \"The capital of France is Paris.\", \"sources\": [\"doc_123\"]}",
"output.mime_type": "application/json",
"session.id": "session_abc123",
"user.id": "user_xyz789"
}
```
## Example: Nested Sub-Chain
```json
{
"openinference.span.kind": "CHAIN",
"input.value": "Summarize this document: ...",
"output.value": "This document discusses..."
}
```
