diff --git a/surfsense_backend/app/automations/triggers/builtin/event/params.py b/surfsense_backend/app/automations/triggers/builtin/event/params.py
new file mode 100644
index 000000000..cd28702c0
--- /dev/null
+++ b/surfsense_backend/app/automations/triggers/builtin/event/params.py
@@ -0,0 +1,23 @@
+"""``EventTriggerParams`` — params for the ``event`` trigger type."""
+
+from __future__ import annotations
+
+from typing import Any
+
+from pydantic import BaseModel, ConfigDict, Field
+
+
+class EventTriggerParams(BaseModel):
+    model_config = ConfigDict(extra="forbid")
+
+    event_type: str = Field(
+        ...,
+        min_length=1,
+        description="Event type to listen for.",
+        examples=["document.indexed"],
+    )
+    filter: dict[str, Any] = Field(
+        default_factory=dict,
+        description="JSON filter matched against the event payload.",
+        examples=[{"document_type": "FILE"}],
+    )
diff --git a/surfsense_backend/tests/unit/automations/triggers/builtin/__init__.py b/surfsense_backend/tests/unit/automations/triggers/builtin/__init__.py
new file mode 100644
index 000000000..e69de29bb
diff --git a/surfsense_backend/tests/unit/automations/triggers/builtin/event/__init__.py b/surfsense_backend/tests/unit/automations/triggers/builtin/event/__init__.py
new file mode 100644
index 000000000..e69de29bb
diff --git a/surfsense_backend/tests/unit/automations/triggers/builtin/event/test_params.py b/surfsense_backend/tests/unit/automations/triggers/builtin/event/test_params.py
new file mode 100644
index 000000000..fef3b0b94
--- /dev/null
+++ b/surfsense_backend/tests/unit/automations/triggers/builtin/event/test_params.py
@@ -0,0 +1,40 @@
+"""``EventTriggerParams`` contract: an event_type to listen for + an optional filter."""
+
+from __future__ import annotations
+
+import pytest
+
+from app.automations.triggers.builtin.event.params import EventTriggerParams
+
+pytestmark = pytest.mark.unit
+
+
+def test_accepts_event_type_and_filter() -> None:
+    params = EventTriggerParams(
+        event_type="document.indexed",
+        filter={"document_type": "FILE"},
+    )
+
+    assert params.event_type == "document.indexed"
+    assert params.filter == {"document_type": "FILE"}
+
+
+def test_filter_defaults_to_empty() -> None:
+    params = EventTriggerParams(event_type="document.indexed")
+
+    assert params.filter == {}
+
+
+def test_event_type_is_required() -> None:
+    with pytest.raises(ValueError):
+        EventTriggerParams(filter={"x": 1})
+
+
+def test_event_type_must_not_be_blank() -> None:
+    with pytest.raises(ValueError):
+        EventTriggerParams(event_type="")
+
+
+def test_extra_keys_are_forbidden() -> None:
+    with pytest.raises(ValueError):
+        EventTriggerParams(event_type="document.indexed", typo=True)