diff --git a/guile/b2-pitr.scm b/guile/b2-pitr.scm
index 56950d8..9cf5447 100644
--- a/guile/b2-pitr.scm
+++ b/guile/b2-pitr.scm
@@ -19,6 +19,33 @@
              (web response)
              (web uri))
 
+(define-exception-type &api-error &external-error
+  make-api-error
+  api-error?
+  (endpoint api-error-endpoint)
+  (status-code api-error-status-code)
+  (body api-error-body))
+
+(define (json-response? res)
+  (eq? 'application/json (car (response-content-type res))))
+
+(define (text-response? res)
+  (string-prefix? "text/"
+                  (symbol->string (car (response-content-type res)))))
+
+(define-syntax check-api-response
+  (syntax-rules ()
+    ((check-api-response endpoint res body-port)
+     (check-api-response endpoint res body-port (<= 100 (response-code res) 399)))
+    ((check-api-response endpoint res body-port ok?)
+     (unless ok?
+       (let ((body (cond
+                    ((json-response? res) (json->scm body-port))
+                    ((text-response? res) (get-string-all body-port))
+                    (else "<binary response body>"))))
+         (close-port body-port)
+         (raise-exception (make-api-error endpoint (response-code res) body)))))))
+
 (define (encode-query alist)
   (fold (match-lambda*
           (((k . v) s)
@@ -32,15 +59,6 @@
         ""
         alist))
 
-(define (http-ok? res)
-  (<= 200 (response-code res) 299))
-
-(define (json-response? res)
-  (eq? 'application/json (car (response-content-type res))))
-
-(define (text-response? res)
-  (string-prefix? "text/"
-                  (symbol->string (car (response-content-type res)))))
 
 ;; We have to override the default handling of the Authorization header as the
 ;; Backblaze API expects just a bare string. The b2_authorize_account endpoint
@@ -53,11 +71,7 @@
   (define auth-url "https://api.backblazeb2.com/b2api/v4/b2_authorize_account")
   (let* ((token (base64-encode (string->bytevector (string-append key-id ":" app-key) "utf-8")))
          (res body (http-get auth-url #:headers `((authorization . ,(string-append "Basic " token))) #:streaming? #t)))
-    (unless (http-ok? res)
-      (raise-exception (make-exception
-                        (make-external-error)
-                        (make-exception-with-message "Error response from b2_authorize_account")
-                        (make-exception-with-irritants res))))
+    (check-api-response "/b2api/v4/b2_authorize_account" res body (and (= 200 (response-code res)) (json-response? res)))
     (json->scm body)))
 
 (define (assoc-ref* alist . keys)
@@ -82,28 +96,16 @@
 (define-method (account-id (cli <b2-client>))
   (assoc-ref (b2-auth-info cli) "accountId"))
 
-(define (check-api-response res body-port err-msg)
-  (unless (http-ok? res)
-    (let ((body (cond
-                 ((json-response? res) (json->scm body-port))
-                 ((text-response? res) (get-string-all body-port))
-                 (else "Binary response body"))))
-      (close-port body-port)
-      (raise-exception (make-exception
-                        (make-external-error)
-                        (make-exception-with-message err-msg)
-                        (make-exception-with-irritants (get-string-all body)))))))
-
-(define* (api-call cli method path #:key query-params payload raw?)
+(define* (api-call cli method endpoint #:key query-params payload raw?)
   (let* ((url (if query-params
-                  (string-append (api-url cli) path "?" (encode-query query-params))
-                  (string-append (api-url cli) path)))
+                  (string-append (api-url cli) endpoint "?" (encode-query query-params))
+                  (string-append (api-url cli) endpoint)))
          (res body-port (method url
                                 #:body (and=> payload scm->json-string)
                                 #:headers `((authorization . ,(auth-token cli))
                                             (content-type . (application/json (charset . "utf-8"))))
                                 #:streaming? #t)))
-    (check-api-response res body-port (string-append "Error from " path))
+    (check-api-response endpoint res body-port)
     (if raw?
         body-port
         (let ((body (cond
@@ -233,6 +235,7 @@ resore these empty files."
 
 (define (main args)
   (define cli (make <b2-client> #:key-id (getenv "BB_KEY_ID") #:app-key (getenv "BB_APP_KEY")))
+
   (define bucket-id (resolve-bucket-id cli "uk-org-1729-server-backups"))
   (define cutoff (* 1000 (time-second (date->time-utc (string->date "2025-06-01 00:00:00+0000" "~Y-~m-~d ~H:~M:~S~z")))))