diff --git a/README.md b/README.md
index cba483a..6ffe3e1 100644
--- a/README.md
+++ b/README.md
@@ -100,7 +100,7 @@ Note that Playground support for importing non-system Frameworks is still a bit
 - `data`
 	- [x] Encoding/Decoding
 	- [x] Arbitrary
-	- [ ] OpenAPI
+	- [x] OpenAPI
 - `included`
 	- [x] Encoding/Decoding
 	- [x] Arbitrary
diff --git a/Sources/JSONAPIOpenAPI/JSONAPITypes+OpenAPI.swift b/Sources/JSONAPIOpenAPI/JSONAPITypes+OpenAPI.swift
index 11934be..619e296 100644
--- a/Sources/JSONAPIOpenAPI/JSONAPITypes+OpenAPI.swift
+++ b/Sources/JSONAPIOpenAPI/JSONAPITypes+OpenAPI.swift
@@ -91,7 +91,9 @@ extension RelationshipType {
 }
 
 extension ToOneRelationship: OpenAPINodeType {
-	// TODO: const for json `type`
+	// NOTE: const for json `type` not supported by OpenAPI 3.0
+	//		Will use "enum" with one possible value for now.
+
 	// TODO: metadata & links
 	static public func openAPINode() throws -> JSONNode {
 		let nullable = Identifiable.self is _Optional.Type
@@ -104,7 +106,9 @@ extension ToOneRelationship: OpenAPINodeType {
 }
 
 extension ToManyRelationship: OpenAPINodeType {
-	// TODO: const for json `type`
+	// NOTE: const for json `type` not supported by OpenAPI 3.0
+	//		Will use "enum" with one possible value for now.
+
 	// TODO: metadata & links
 	static public func openAPINode() throws -> JSONNode {
 		return .object(.init(format: .generic,