diff --git a/src/inkwell/accounts_api.py b/src/inkwell/accounts_api.py
index 104c543..1d93a6a 100644
--- a/src/inkwell/accounts_api.py
+++ b/src/inkwell/accounts_api.py
@@ -6,7 +6,6 @@ What a reset link is, and how it is used, is in `password_resets.py`.
 from __future__ import annotations
 
 import logging
-import uuid
 
 from quart import Blueprint, g, jsonify, request
 from sqlalchemy import select
@@ -18,6 +17,7 @@ from .db import session_scope
 from .models.user import User
 from .password_resets import issue
 from .proxy import client_address
+from .responses import not_found, parse_uuid
 
 bp = Blueprint("accounts", __name__, url_prefix="/api/accounts")
 
@@ -46,14 +46,13 @@ async def list_accounts():
 @bp.post("/<account_id>/reset-link")
 @require_admin
 async def create_reset_link(account_id: str):
-    try:
-        uid = uuid.UUID(account_id)
-    except ValueError:
-        return jsonify({"error": "not found"}), 404
+    uid = parse_uuid(account_id)
+    if uid is None:
+        return not_found()
     async with session_scope() as db:
         user = await db.get(User, uid)
         if user is None:
-            return jsonify({"error": "not found"}), 404
+            return not_found()
         token, expires_at = await issue(db, uid, g.user_id)
         await db.commit()
         email = user.email
diff --git a/src/inkwell/app.py b/src/inkwell/app.py
index 9c1c412..667b5b2 100644
--- a/src/inkwell/app.py
+++ b/src/inkwell/app.py
@@ -23,6 +23,7 @@ from .invites_api import bp as invites_bp
 from .labels import bp as labels_bp
 from .notes import bp as notes_bp
 from .proxy import is_https
+from .responses import json_error, not_found
 from .retention import run_sweeper
 from .settings import MAX_BODY_MB, get_public_config, get_setting, load_or_create_secret_key, refresh_live
 from .settings_api import bp as settings_bp
@@ -225,13 +226,13 @@ def create_app() -> Quart:
     @app.get("/<path:path>")
     async def spa(path: str):
         if path.startswith("api/"):
-            return jsonify({"error": "not found"}), 404
+            return not_found()
         candidate = os.path.join(STATIC_DIR, path)
         if path and os.path.isfile(candidate):
             return await send_from_directory(STATIC_DIR, path)
         index = os.path.join(STATIC_DIR, "index.html")
         if os.path.isfile(index):
             return await send_from_directory(STATIC_DIR, "index.html")
-        return jsonify({"error": "frontend not built"}), 404
+        return json_error("frontend not built", 404)
 
     return app
diff --git a/src/inkwell/invites_api.py b/src/inkwell/invites_api.py
index 0420fea..59c1111 100644
--- a/src/inkwell/invites_api.py
+++ b/src/inkwell/invites_api.py
@@ -5,7 +5,6 @@ What an invite is, and how it is redeemed, is in `invites.py`.
 from __future__ import annotations
 
 import logging
-import uuid
 from datetime import datetime, timedelta, timezone
 
 from quart import Blueprint, g, jsonify, request
@@ -19,6 +18,7 @@ from .invites import MAX_DAYS, lifetime_days, serialize
 from .models.invite import Invite
 from .models.user import User
 from .proxy import client_address
+from .responses import json_error, not_found, parse_uuid
 from .security import generate_token, hash_token
 
 bp = Blueprint("invites", __name__, url_prefix="/api/invites")
@@ -33,10 +33,10 @@ async def create_invite():
     data = await request.get_json(silent=True) or {}
     email = (data.get("email") or "").strip().lower() or None
     if email is not None and "@" not in email:
-        return jsonify({"error": "that doesn't look like an email address"}), 400
+        return json_error("that doesn't look like an email address", 400)
     days = lifetime_days(data.get("days"))
     if days is None:
-        return jsonify({"error": f"an invite lasts between 1 and {MAX_DAYS} days"}), 400
+        return json_error(f"an invite lasts between 1 and {MAX_DAYS} days", 400)
 
     token = generate_token()
     now = datetime.now(timezone.utc)
@@ -82,15 +82,14 @@ async def list_invites():
 @bp.delete("/<invite_id>")
 @require_admin
 async def revoke_invite(invite_id: str):
-    try:
-        iid = uuid.UUID(invite_id)
-    except ValueError:
-        return jsonify({"error": "not found"}), 404
+    iid = parse_uuid(invite_id)
+    if iid is None:
+        return not_found()
     now = datetime.now(timezone.utc)
     async with session_scope() as db:
         invite = await db.get(Invite, iid)
         if invite is None:
-            return jsonify({"error": "not found"}), 404
+            return not_found()
         # A used invite has done its work and its record stays as it is; an already
         # revoked one keeps its first revocation time.
         if invite.redeemed_at is None and invite.revoked_at is None:
diff --git a/src/inkwell/settings_api.py b/src/inkwell/settings_api.py
index cf5be5b..2af9434 100644
--- a/src/inkwell/settings_api.py
+++ b/src/inkwell/settings_api.py
@@ -64,9 +64,7 @@ async def test_email():
     async with session_scope() as db:
         cfg = await mail_settings(db)
         if cfg is None:
-            return jsonify(
-                {"error": "Email is off: it needs an SMTP server, a from address and the public address."}
-            ), 400
+            return json_error("Email is off: it needs an SMTP server, a from address and the public address.", 400)
         admin = await db.get(User, g.user_id)
         site = await get_setting(db, "site_name")
     try: