diff --git a/pyproject.toml b/pyproject.toml
index 8572e99..81a492c 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -40,6 +40,7 @@ dependencies = [
     "starfile",
     "scipy",
     "mrcfile",
+    "pydantic",
     "mmdf",
     "requests",
     "torch-fourier-filter"
diff --git a/src/ttsim3d/input_models.py b/src/ttsim3d/input_models.py
new file mode 100644
index 0000000..f218447
--- /dev/null
+++ b/src/ttsim3d/input_models.py
@@ -0,0 +1,24 @@
+"""Pydantic models for input parameters."""
+
+from pydantic import BaseModel
+
+
+class SimulationParams(BaseModel):
+    """Parameters for the simulation."""
+
+    pdb_filename: str
+    output_filename: str
+    sim_volume_shape: tuple[int, int, int] = (400, 400, 400)
+    sim_pixel_spacing: float = 0.95
+    num_frames: int = 50
+    fluence_per_frame: float = 1
+    beam_energy_kev: int = 300
+    dose_weighting: bool = True
+    dose_B: float = -1
+    apply_dqe: bool = True
+    mtf_filename: str
+    b_scaling: float = 0.5
+    added_B: float = 0.0
+    upsampling: int = -1
+    gpu_id: int = -999
+    modify_signal: int = 1
diff --git a/src/ttsim3d/run_ttsim3d.py b/src/ttsim3d/run_ttsim3d.py
index ce5e80a..f2c3402 100644
--- a/src/ttsim3d/run_ttsim3d.py
+++ b/src/ttsim3d/run_ttsim3d.py
@@ -1,13 +1,15 @@
 """Simple run script."""
 
+from ttsim3d.input_models import SimulationParams
 from ttsim3d.simulate3d import simulate3d
 
 
 def main() -> None:
     """A test function to run the simulate3d function from the ttsim3d package."""
-    simulate3d(
+    params = SimulationParams(
         pdb_filename="/Users/josh/git/2dtm_tests/simulator/parsed_6Q8Y_whole_LSU_match3.pdb",
         output_filename="/Users/josh/git/2dtm_tests/simulator/simulated_6Q8Y_whole_LSU_match3.mrc",
+        mtf_filename="/Users/josh/git/2dtm_tests/simulator/mtf_k2_300kV.star",
         sim_volume_shape=(400, 400, 400),
         sim_pixel_spacing=0.95,
         num_frames=50,
@@ -16,14 +18,15 @@ def main() -> None:
         dose_weighting=True,
         dose_B=-1,
         apply_dqe=True,
-        mtf_filename="/Users/josh/git/2dtm_tests/simulator/mtf_k2_300kV.star",
         b_scaling=0.5,
         added_B=0.0,
         upsampling=-1,
         gpu_id=-999,
-        modify_signal=1,  # This is how to apply the dose weighting.
+        modify_signal=1,
     )
 
+    simulate3d(**params.model_dump())
+
 
 if __name__ == "__main__":
     main()