Generate new Teiid Project with no changes to the defaults. Right-Click on project => Import => Teiid Designer => Web Service Source >> Source and View Model (REST) New Button in REST Web Service Source => Next Parameters: Connection URL: "http: //md5.jsontest.com/" Response Type "JSON" Security Type "None" There is no way to define Parameters here Test connection succedes Ciick Finish The REST Web Service Source Selection Dialog shows the message No REST Response Files Selected for Import because the response is empty. To add the actual parameter click on Edit . Under Connection Properties there is an Add new Parameter button now. Click it and try to add a parameter with an underscore character in its name. It tells you <Missing message for key "AddParameterDialog_invalidParametersName" in: org.teiid.designer.datatools.ui.i18n> . Instead add parameter "text" with no default value and Type "Query". Once saved the error message "XML File Parsing Error" "Parsing Error: The markup in the document following the root element must be well-formed." is shown. Once again click Edit , select the "text"-Parameter in the listview and delete it using the Remove Parameter button. It does not matter whether you click Apply or Ok , the change to the parameter is not persisted.