Netlogo web extension "expected a literal value"

I have a model which is meant to interact with an api using web extension. So after each move, I will send my current location, heading to the API.

This is the code I am using:

to follow-path
  let choice web:make-request "http://127.0.0.1:8000/predict_get" "GET" [] []
  (ifelse
    choice = 0 [
      forward 1
    ]
    choice = 1 [
      right 90
    ]
    choice = 2 [
      left 90
    ]
    ; elsecommands
    [
      stop
  ])
  let data web:make-request "http://127.0.0.1:8000/netlogo" "POST" [["data" (list xcor ycor heading)]] []
end

to move-agent
  ask turtle (count turtles - 1) [follow-path]
end

Then when I checked, it said "Expected a literal value" at the list part. How can I post the list of data to the api correctly ?

I think you are struggling with the [[ ]] notation in NetLogo. This notation allows creating lists with only actual values but doesn't work with variables.

I recommend you to test the following explanation in the Command Center for an illustration.

Creating lists with just values:

The following code: show [ [ "name" "john"] ["surname" "doe"] ]

Would print the following outcome: [["name" "john"] ["surname" "doe"]]

This way, you can create lists with literal values. However, you cannot use variables instead of literal values. For example, the following code would give the same error you are seeing in your code:

let name "john"
let surname "doe"
show [ [ "name" name] ["surname" surname] ]

Creating lists with variables

You should use the list primitive in a nested manner to create your arguments for the web:make-request command to solve your problam.

Here's an example usage:

let name "john"
let surname "doe"
show (list (list "name" name) (list "surname" surname))

which would print:

[["name" "john"] ["surname" "doe"]]