InfluxDB/Telegraf Webhook JSON error

It depends whether you can accept your numeric values to be wrapped in double quotes or not.
If so, you can use Custom JSON, otherwise you need to use Custom Body like this

And write the code somewhere along the line of this

  char data[255];
  snprintf(data
          ,sizeof(data) 
          ,"{\"id\": \"%s\" ,\"loc\": \"%s\", \"cap\": \"%d\"}"
          ,            id   ,           loc  ,           i++
          );
  Particle.publish("RequestBin", data, PRIVATE);

With a custom JSON/Body template you can keep the data used for the actual event publish as short as can be, since the static extras (like your tags and values “containers” or any other static field you may be needing) can be added by the cloud via the template specification.

So the above code produces this event


and the webhook integration results in this data on the receiving server
image