Does anyone know how to reference the 'input' key-value from an API request in the workflow canvas start node?

curl --location --request POST ‘https://api.dify.ai/v1/chat-messages’
–header ‘Authorization: Bearer ENTER-YOUR-SECRET-KEY’
–header ‘Content-Type: application/json’
–data-raw ‘{
“inputs”: {},
“query”: “eh”,
“response_mode”: “streaming”,
“conversation_id”: “1c7e55fb-1ba2-4e10-81b5-30addcea2276”,
“user”: “abc-123”
}’
I want to reference the “input” value in the start node of the canvas, but I couldn’t find it after reviewing the official documentation. Can I create a string field “input1” in the request and then create an input variable in the start node?