Merge pull request #1074 from OAI/dm/972

Added paragraph about markdown

Author: darrelmiller

versions/3.0.md

@@ -27,6 +27,7 @@ Additional utilities can also take advantage of the resulting files, such as tes
 	- [Format](#format)
 	- [File Structure](#fileStructure)
 	- [Data Types](#dataTypes)
+	- [Rich Text Formatting](#richText)
 	- [Relative References In URLs](#relativeReferences)
 	- [Schema](#schema)
 		- [OpenAPI Object](#oasObject)
@@ -165,6 +166,10 @@ date | `string` | `date` | As defined by `full-date` - [RFC3339](http://xml2rfc.
 dateTime | `string` | `date-time` | As defined by `date-time` - [RFC3339](http://xml2rfc.ietf.org/public/rfc/html/rfc3339.html#anchor14)
 password | `string` | `password` | Used to hint UIs the input needs to be obscured.
 
+### <a name="richText"></a>Rich Text Formatting
+Throughout the specification `description` fields are noted as supporting CommonMark markdown formatting.
+OpenAPI compliant tooling MUST support [CommonMark 0.27](http://spec.commonmark.org/0.27/). 
+
 ### <a name="relativeReferences"></a>Relative References in URLs
 
 Unless specified otherwise, all properties that are URLs MAY be relative references as defined by [RFC 3986](https://tools.ietf.org/html/rfc3986#section-4.2).