diff --git a/src/climatevision/api/main.py b/src/climatevision/api/main.py
index 729b213..d873599 100644
--- a/src/climatevision/api/main.py
+++ b/src/climatevision/api/main.py
@@ -109,8 +109,14 @@ class PredictRequest(BaseModel):
     kind: str = Field(default="demo")
     analysis_type: AnalysisType = Field(default="deforestation")
     bbox: Optional[list[float]] = None
-    start_date: Optional[str] = None
-    end_date: Optional[str] = None
+    start_date: Optional[str] = Field(
+        default=None,
+        description="Start date in YYYY-MM-DD format. Must be earlier than end_date.",
+    )
+    end_date: Optional[str] = Field(
+        default=None,
+        description="End date in YYYY-MM-DD format. Must be later than start_date.",
+    )
 
     @field_validator("bbox")
     @classmethod
@@ -563,9 +569,6 @@ async def predict_json(
         org: dict[str, Any] = Depends(require_api_key),
     ) -> dict[str, Any]:
         """Run prediction using bounding box and date range."""
-        if body.start_date and body.end_date and body.start_date > body.end_date:
-            raise HTTPException(status_code=400, detail="start_date must be before end_date")
-
         created_at = _utc_now_iso()
         bbox_json = json.dumps(body.bbox) if body.bbox else None
 
diff --git a/tests/test_api.py b/tests/test_api.py
index 1593b40..da9c49c 100644
--- a/tests/test_api.py
+++ b/tests/test_api.py
@@ -1,5 +1,7 @@
 """Tests for ClimateVision API endpoints."""
 
+from unittest.mock import patch
+
 import pytest
 from fastapi.testclient import TestClient
 
@@ -40,3 +42,63 @@ def test_predict_json_accepts_dev_key(client: TestClient) -> None:
     )
     # Should pass auth; inference may fail due to missing models/GEE
     assert response.status_code in (200, 500)
+
+
+def test_predict_valid_date_range_reaches_inference(client: TestClient) -> None:
+    """POST /api/predict with valid date range should reach the inference layer."""
+    payload = {
+        "bbox": [-60.0, -15.0, -45.0, -5.0],
+        "start_date": "2023-01-01",
+        "end_date": "2023-06-30",
+        "analysis_type": "deforestation",
+    }
+    fake_result = {
+        "region": {"bbox": payload["bbox"]},
+        "inference": {"forest_percentage": 72.3},
+        "analysis_type": "deforestation",
+    }
+    with patch(
+        "climatevision.api.main.run_inference_from_gee", return_value=fake_result
+    ) as mock_infer:
+        response = client.post(
+            "/api/predict",
+            json=payload,
+            headers={"X-API-Key": "cv_dev"},
+        )
+    assert response.status_code == 200
+    mock_infer.assert_called_once()
+
+
+def test_predict_reversed_date_range_returns_422(client: TestClient) -> None:
+    """POST /api/predict with start_date > end_date should return 422."""
+    payload = {
+        "bbox": [-60.0, -15.0, -45.0, -5.0],
+        "start_date": "2026-06-01",
+        "end_date": "2026-01-01",
+        "analysis_type": "deforestation",
+    }
+    response = client.post(
+        "/api/predict",
+        json=payload,
+        headers={"X-API-Key": "cv_dev"},
+    )
+    assert response.status_code == 422
+    body = response.json()
+    error_messages = [e["msg"] for e in body["detail"]]
+    assert any("start_date" in msg or "end_date" in msg for msg in error_messages)
+
+
+def test_predict_equal_dates_returns_422(client: TestClient) -> None:
+    """POST /api/predict with start_date == end_date should return 422."""
+    payload = {
+        "bbox": [-60.0, -15.0, -45.0, -5.0],
+        "start_date": "2023-06-01",
+        "end_date": "2023-06-01",
+        "analysis_type": "deforestation",
+    }
+    response = client.post(
+        "/api/predict",
+        json=payload,
+        headers={"X-API-Key": "cv_dev"},
+    )
+    assert response.status_code == 422