Values created by the CandidType function Func correspond to the Candid type func, are inferred to be TypeScript [Principal, string] tuples, and will be decoded into JavaScript array with two elements at runtime.

The first element is an @dfinity/principal and the second is a JavaScript string. The @dfinity/principal represents the principal of the canister/service where the function exists, and the string represents the function's name.

A func acts as a callback, allowing the func receiver to know which canister instance and method must be used to call back.

TypeScript or JavaScript:

import { Canister, Func, Principal, query, text } from 'azle';

const BasicFunc = Func([text], text, 'query');

export default Canister({
    getBasicFunc: query([], BasicFunc, () => {
        return [
    printBasicFunc: query([BasicFunc], BasicFunc, (basicFunc) => {
        console.log(typeof basicFunc);
        return basicFunc;


service : () -> {
    getBasicFunc : () -> (func (text) -> (text) query) query;
    printBasicFunc : (func (text) -> (text) query) -> (
        func (text) -> (text) query,
      ) query;


dfx canister call candid_canister printBasicFunc '(func "r7inp-6aaaa-aaaaa-aaabq-cai".getBasicFunc)'
(func "r7inp-6aaaa-aaaaa-aaabq-cai".getBasicFunc)