diff --git a/api/app/models/__pycache__/terrain.cpython-313.pyc b/api/app/models/__pycache__/terrain.cpython-313.pyc
index 903934e..9208ca5 100644
Binary files a/api/app/models/__pycache__/terrain.cpython-313.pyc and b/api/app/models/__pycache__/terrain.cpython-313.pyc differ
diff --git a/api/app/models/terrain.py b/api/app/models/terrain.py
index 54d3577..7918e7a 100644
--- a/api/app/models/terrain.py
+++ b/api/app/models/terrain.py
@@ -51,6 +51,8 @@ class LosRequest(BaseModel):
 class Obstruction(BaseModel):
     distance_m: float
     clearance_m: float
+    fresnel_radius_m: float
+    required_clearance_m: float
     type: Literal["terrain", "building", "canopy"]
 
 
@@ -60,5 +62,9 @@ class LosResponse(BaseModel):
     first_fresnel_clearance_pct: float
     worst_obstruction: Obstruction | None
     obstructions: list[Obstruction]
+    geometric_obstructions: list[Obstruction]
+    fresnel_violations_count: int
+    geometric_obstructions_count: int
+    building_obstructions_count: int
     diffraction_loss_db: float
     profile_ref: str
diff --git a/api/app/services/__pycache__/terrain.cpython-313.pyc b/api/app/services/__pycache__/terrain.cpython-313.pyc
index 208fab6..a3e2e76 100644
Binary files a/api/app/services/__pycache__/terrain.cpython-313.pyc and b/api/app/services/__pycache__/terrain.cpython-313.pyc differ
diff --git a/api/app/services/terrain.py b/api/app/services/terrain.py
index 3431d1a..779c53f 100644
--- a/api/app/services/terrain.py
+++ b/api/app/services/terrain.py
@@ -7,7 +7,7 @@ from sqlalchemy.orm import Session
 from app.config import get_settings
 from app.core import dem
 from app.core.diffraction import deygout
-from app.core.fresnel import los_analysis
+from app.core.fresnel import LosSample, los_analysis
 from app.core.geo import GeoPoint, PathPoint, linestring_geojson, sample_path
 from app.core.surface import build_surface_profile
 from app.models.terrain import (
@@ -102,19 +102,34 @@ def los(
         request.frequency_mhz * 1_000_000,
     )
 
-    def convert(sample: object) -> Obstruction:
+    def convert(sample: LosSample) -> Obstruction:
         return Obstruction(
             distance_m=sample.distance_m,
             clearance_m=sample.clearance_m,
+            fresnel_radius_m=sample.fresnel_radius_m,
+            required_clearance_m=sample.required_clearance_m,
             type=sample.obstruction_type,
         )
 
+    geometric_obstructions = [
+        sample for sample in result.obstructions if sample.clearance_m < 0
+    ]
+    building_obstructions = [
+        sample
+        for sample in geometric_obstructions
+        if sample.obstruction_type == "building"
+    ]
+
     return LosResponse(
         los_clear=result.los_clear,
         geometric_los=result.geometric_los,
         first_fresnel_clearance_pct=result.first_fresnel_clearance_pct,
         worst_obstruction=convert(result.worst_sample) if result.worst_sample else None,
         obstructions=[convert(sample) for sample in result.obstructions],
+        geometric_obstructions=[convert(sample) for sample in geometric_obstructions],
+        fresnel_violations_count=len(result.obstructions),
+        geometric_obstructions_count=len(geometric_obstructions),
+        building_obstructions_count=len(building_obstructions),
         diffraction_loss_db=diffraction_loss,
         profile_ref=f"inline:{profile_request.samples}",
     )
diff --git a/api/tests/__pycache__/test_api.cpython-313-pytest-9.0.3.pyc b/api/tests/__pycache__/test_api.cpython-313-pytest-9.0.3.pyc
index 141eb89..b5c6efa 100644
Binary files a/api/tests/__pycache__/test_api.cpython-313-pytest-9.0.3.pyc and b/api/tests/__pycache__/test_api.cpython-313-pytest-9.0.3.pyc differ
diff --git a/api/tests/test_api.py b/api/tests/test_api.py
index b94fc84..3a1288c 100644
--- a/api/tests/test_api.py
+++ b/api/tests/test_api.py
@@ -45,6 +45,31 @@ def test_elevation_returns_not_implemented_without_dem() -> None:
     assert response.status_code == 501
 
 
+def test_los_endpoint_returns_obstruction_summary_fields() -> None:
+    response = client.post(
+        "/api/v1/terrain/los",
+        json={
+            "tx": {"lat": 59.935, "lon": 30.305, "height_agl": 30},
+            "rx": {"lat": 59.945, "lon": 30.325, "height_agl": 2},
+            "frequency_mhz": 433,
+            "fresnel_clearance": 0.6,
+            "include_buildings": False,
+            "include_canopy": False,
+            "k_factor": 1.333,
+            "samples": 16,
+        },
+    )
+    assert response.status_code == 200
+    data = response.json()
+    assert "obstructions" in data
+    assert "geometric_obstructions" in data
+    assert data["fresnel_violations_count"] == len(data["obstructions"])
+    assert data["geometric_obstructions_count"] == len(data["geometric_obstructions"])
+    assert data["building_obstructions_count"] == len(
+        [item for item in data["geometric_obstructions"] if item["type"] == "building"]
+    )
+
+
 def test_manual_link_budget_endpoint() -> None:
     response = client.post(
         "/api/v1/link/budget",