from https://github.com/swagger-api/swagger-ui/issues/3817

gistfile1.txt

openapi: 3.0.0
info:
  title: math.js web service
  version: '1.0'
servers:
  - url: http://api.mathjs.org/v1
paths:
  /:
    get:
      summary: Evaluates an expression and returns result as plain text
      parameters:
        - in: query
          name: expr
          required: true
          description: The expression to be evaluated
          schema:
            type: string
            example: 2+3*sqrt(4)
      responses:
        '200':
          description: OK
          content:
            text/html:
              schema:
                type: string