diff --git a/steward/mcp/tools/monitors.py b/steward/mcp/tools/monitors.py
index 2224f82..2cbc693 100644
--- a/steward/mcp/tools/monitors.py
+++ b/steward/mcp/tools/monitors.py
@@ -6,6 +6,7 @@ import json
 from sqlalchemy import select
 
 from steward.core import renames
+from steward.mcp._context import mcp_app
 from steward.models.hosts import Host
 from steward.models.monitors import MONITOR_TYPE_VALUES, Monitor
 from steward.models.users import UserRole
@@ -27,6 +28,15 @@ def _state(m: Monitor, latest) -> str:
     return "up" if latest.is_up else "down"
 
 
+def _interval(m: Monitor) -> dict:
+    """How often a monitor runs: its own interval, or the global one it
+    follows when it has none (#5433), and which."""
+    if m.check_interval_seconds:
+        return {"check_interval_s": m.check_interval_seconds, "interval_from": "monitor"}
+    return {"check_interval_s": int(mcp_app().config.get("MONITORS_POLL_INTERVAL", 60)),
+            "interval_from": "global"}
+
+
 def _tls_days(latest) -> float | None:
     if latest is None or latest.tls_expires_at is None:
         return None
@@ -112,8 +122,10 @@ async def get_monitor(monitor: str, failures: int = 10) -> dict:
       newest first, each with its error message.
 
     `heartbeat` is its last 30 checks oldest-first as a string, "+" up and "-"
-    down, to show a flapping check at a glance. Header values in an HTTP
-    monitor's configuration are redacted.
+    down, to show a flapping check at a glance. `check_interval_s` is how
+    often it runs; `interval_from` says whether that is its own setting
+    ("monitor") or the global monitors interval it follows ("global").
+    Header values in an HTTP monitor's configuration are redacted.
     """
     failures = clamp_limit(failures, 10, 50)
     async with db_session() as db:
@@ -123,7 +135,7 @@ async def get_monitor(monitor: str, failures: int = 10) -> dict:
         failed = await monitor_svc.recent_failures(db, m.id, failures)
     return {
         **_row(m, st, host_names),
-        "check_interval_s": m.check_interval_seconds or None,
+        **_interval(m),
         "config": _config(m),
         "heartbeat": "".join("+" if r.is_up else "-" for r in st["recent"]),
         "recent_failures": [
@@ -156,7 +168,7 @@ def _saved(m: Monitor, host_names: dict[str, str]) -> dict:
         "target": redact_url(m.target),
         "host_name": host_names.get(m.host_id) if m.host_id else None,
         "enabled": m.enabled,
-        "check_interval_s": m.check_interval_seconds or None,
+        **_interval(m),
         "config": _config(m),
         "next": f'get_monitor(monitor="{m.id}")',
     }
diff --git a/tests/integration/test_mcp_monitoring_writes.py b/tests/integration/test_mcp_monitoring_writes.py
index f55ad42..6c773ac 100644
--- a/tests/integration/test_mcp_monitoring_writes.py
+++ b/tests/integration/test_mcp_monitoring_writes.py
@@ -76,6 +76,9 @@ def test_monitor_rule_ack_and_maintenance_writes(app):
         assert made["target"] == "https://nas.lan" and made["host_name"] == host_name
         assert made["config"]["headers"] == {"Authorization": "<redacted>"}
         assert made["config"]["verify_ssl"] is True
+        # No interval of its own: it says which it follows, and how often (#5433).
+        assert (made["check_interval_s"], made["interval_from"]) == (
+            int(app.config.get("MONITORS_POLL_INTERVAL", 60)), "global")
 
         # ── rules ──────────────────────────────────────────────────────────
         opts = await a.get_alert_rule_options("http")
@@ -100,7 +103,9 @@ def test_monitor_rule_ack_and_maintenance_writes(app):
         assert renamed["carried"]["from"] == mon_name and renamed["carried"]["rules"] == 1
         async with app.db_sessionmaker() as s:
             assert (await s.get(AlertRule, rule["rule_id"])).resource_name == f"{mon_name}-2"
-        assert "carried" not in await m.update_monitor(f"{mon_name}-2", check_interval_s=30)
+        own = await m.update_monitor(f"{mon_name}-2", check_interval_s=30)
+        assert "carried" not in own
+        assert (own["check_interval_s"], own["interval_from"]) == (30, "monitor")
         # Another http monitor may not take the same name: they would share one history.
         with pytest.raises(ValueError, match="already named"):
             await m.create_monitor(f"{mon_name}-2", "http", "other.lan")