Reply with 200 from Nginx config without serving a file

location / {
return 200 'gangnam style!';
# because default content-type is application/octet-stream,
# browser will offer to "save the file"...
# if you want to see reply in browser, uncomment next line
# add_header Content-Type text/plain;
}

location / {
return 200 'your json string';
add_header Content-Type text/plain;
}