Helper function to restrict contract calls

;; Check if caller is a standard principal (user wallet)
(define-private (is-standard-principal-call)
  (is-none (get name (unwrap! (principal-destruct? contract-caller) false)))
)

;; Public function restricted to direct user calls
(define-public (user-only-function (amount uint))
  (begin
    (asserts! (is-standard-principal-call) (err u401))
    ;; Function logic here
    (ok true)
  )
)

Use cases

• Preventing contract-to-contract reentrancy attacks
• Ensuring human-initiated transactions for governance
• Restricting token minting to direct user actions
• Protecting admin functions from automated calls

Key concepts

Principal types in Clarity:

• Standard principals: User wallets (SP/ST addresses)
• Contract principals: Deployed contracts (address.contract-name)
• contract-caller: The immediate caller of the current function
• tx-sender: The original transaction initiator