diff --git a/Cargo.lock b/Cargo.lock
index 117bdbee9..fd91ac569 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -686,7 +686,6 @@ checksum = "43da5946c66ffcc7745f48db692ffbb10a83bfe0afd96235c5c2a4fb23994929"
 name = "cuboid"
 version = "0.1.0"
 dependencies = [
- "anyhow",
  "clap",
  "fj",
 ]
@@ -1364,7 +1363,6 @@ checksum = "dfa686283ad6dd069f105e5ab091b04c62850d3e4cf5d67debad1933f55023df"
 name = "holes"
 version = "0.1.0"
 dependencies = [
- "anyhow",
  "clap",
  "cuboid",
  "fj",
@@ -3430,7 +3428,6 @@ dependencies = [
 name = "spacer"
 version = "0.1.0"
 dependencies = [
- "anyhow",
  "clap",
  "fj",
 ]
@@ -3474,7 +3471,6 @@ checksum = "a8f112729512f8e442d81f95a8a7ddf2b7c6b8a1a6f509a95864142b30cab2d3"
 name = "star"
 version = "0.1.0"
 dependencies = [
- "anyhow",
  "clap",
  "fj",
 ]
diff --git a/crates/fj/src/instance.rs b/crates/fj/src/instance.rs
index e650f9507..2a937ccfa 100644
--- a/crates/fj/src/instance.rs
+++ b/crates/fj/src/instance.rs
@@ -46,53 +46,8 @@ impl Instance {
         for<'r> (&'r M, Tolerance): Triangulate,
         for<'r> &'r M: BoundingVolume<3>,
     {
-        tracing_subscriber::registry()
-            .with(tracing_subscriber::fmt::layer())
-            .with(tracing_subscriber::EnvFilter::from_default_env())
-            .init();
-
         let args = Args::parse();
-
-        if !args.ignore_validation {
-            self.core.layers.validation.take_errors()?;
-        }
-
-        let aabb = model.aabb(&self.core.layers.geometry).unwrap_or(Aabb {
-            min: Point::origin(),
-            max: Point::origin(),
-        });
-
-        let tolerance = match args.tolerance {
-            None => {
-                // Compute a reasonable default for the tolerance value. To do
-                // this, we just look at the smallest non-zero extent of the
-                // bounding box and divide that by some value.
-
-                let mut min_extent = Scalar::MAX;
-                for extent in aabb.size().components {
-                    if extent > Scalar::ZERO && extent < min_extent {
-                        min_extent = extent;
-                    }
-                }
-
-                let tolerance = min_extent / Scalar::from_f64(1000.);
-                Tolerance::from_scalar(tolerance)?
-            }
-            Some(user_defined_tolerance) => user_defined_tolerance,
-        };
-
-        let tri_mesh = (model, tolerance).triangulate(&mut self.core);
-
-        if let Some(path) = args.export {
-            export::export(tri_mesh.all_triangles(), &path)?;
-            return Ok(());
-        }
-
-        make_viewer_and_spawn_thread(|viewer| {
-            viewer.display_model(tri_mesh);
-        })?;
-
-        Ok(())
+        self.process_model_args(model, args)
     }
 
     /// Process a model with pre-parsed arguments
diff --git a/models/cuboid/Cargo.toml b/models/cuboid/Cargo.toml
index f5b334b92..aefaaeaf8 100644
--- a/models/cuboid/Cargo.toml
+++ b/models/cuboid/Cargo.toml
@@ -3,11 +3,6 @@ name = "cuboid"
 version = "0.1.0"
 edition = "2021"
 
-[[bin]]
-name = "cuboid"
-path = "src/main.rs"
-
 [dependencies]
 fj = { path = "../../crates/fj" }
 clap = { version = "4.5", features = ["derive"] }
-anyhow = "1.0"
diff --git a/models/cuboid/src/main.rs b/models/cuboid/src/main.rs
index 5dd122db6..d0a883344 100644
--- a/models/cuboid/src/main.rs
+++ b/models/cuboid/src/main.rs
@@ -1,30 +1,28 @@
 use clap::Parser;
-use fj::{Args, Instance};
 
 #[derive(Parser)]
 struct Parameters {
-    /// Size of the cuboid, as a comma-separated vector `x,y,z`
-    #[arg(long, value_parser = parse_vector_3, default_value = "1,1,1")]
-    size: [f64; 3],
+    /// Size of the cuboid along the x-axis
+    #[arg(long, default_value = "3.0")]
+    x: f64,
+
+    /// Size of the cuboid along the y-axis
+    #[arg(long, default_value = "2.0")]
+    y: f64,
+
+    /// Size of the cuboid along the z-axis
+    #[arg(long, default_value = "1.0")]
+    z: f64,
 
     #[command(flatten)]
-    fj: Args,
+    fj: fj::Args,
 }
 
-fn parse_vector_3(arg: &str) -> anyhow::Result<[f64; 3]> {
-    Ok(arg
-        .split(',')
-        .map(str::parse)
-        .collect::<Result<Vec<f64>, _>>()?
-        .as_slice()
-        .try_into()?)
-}
-
-fn main() -> anyhow::Result<()> {
-    let mut fj = Instance::new();
+fn main() -> fj::Result {
+    let mut fj = fj::Instance::new();
     let params = Parameters::parse();
 
-    let model = cuboid::model(params.size, &mut fj.core);
+    let model = cuboid::model([params.x, params.y, params.z], &mut fj.core);
     fj.process_model_args(&model, params.fj)?;
 
     Ok(())
diff --git a/models/holes/Cargo.toml b/models/holes/Cargo.toml
index a51f67b6d..98c3a2420 100644
--- a/models/holes/Cargo.toml
+++ b/models/holes/Cargo.toml
@@ -3,12 +3,7 @@ name = "holes"
 version = "0.1.0"
 edition = "2021"
 
-[[bin]]
-name = "holes"
-path = "src/main.rs"
-
 [dependencies]
 fj = { path = "../../crates/fj" }
 clap = { version = "4.5", features = ["derive"] }
-anyhow = "1.0"
 cuboid = { path = "../cuboid" }
diff --git a/models/holes/src/lib.rs b/models/holes/src/lib.rs
index 9724d1ffe..013cbdef8 100644
--- a/models/holes/src/lib.rs
+++ b/models/holes/src/lib.rs
@@ -13,7 +13,7 @@ pub fn model(radius: impl Into<Scalar>, core: &mut fj::core::Core) -> Solid {
     let radius = radius.into();
 
     let size = radius * 4.;
-    let cuboid = ::cuboid::model([size * 2., size, size], core);
+    let cuboid = cuboid::model([size * 2., size, size], core);
 
     cuboid.update_shell(
         cuboid.shells().only(),
diff --git a/models/holes/src/main.rs b/models/holes/src/main.rs
index 2c2e83f34..bf32325f5 100644
--- a/models/holes/src/main.rs
+++ b/models/holes/src/main.rs
@@ -1,6 +1,4 @@
-use anyhow::Result;
 use clap::Parser;
-use fj::{Args, Instance};
 
 #[derive(Parser)]
 struct Parameters {
@@ -9,11 +7,11 @@ struct Parameters {
     radius: f64,
 
     #[command(flatten)]
-    fj: Args,
+    fj: fj::Args,
 }
 
-fn main() -> Result<()> {
-    let mut fj = Instance::new();
+fn main() -> fj::Result {
+    let mut fj = fj::Instance::new();
     let params = Parameters::parse();
 
     let model = holes::model(params.radius, &mut fj.core);
diff --git a/models/spacer/Cargo.toml b/models/spacer/Cargo.toml
index 1a321051b..6196e97c0 100644
--- a/models/spacer/Cargo.toml
+++ b/models/spacer/Cargo.toml
@@ -3,11 +3,6 @@ name = "spacer"
 version = "0.1.0"
 edition = "2021"
 
-[[bin]]
-name = "spacer"
-path = "src/main.rs"
-
 [dependencies]
 fj = { path = "../../crates/fj" }
 clap = { version = "4.5", features = ["derive"] }
-anyhow = "1.0"
diff --git a/models/spacer/src/main.rs b/models/spacer/src/main.rs
index 26d0bc78b..7ec06b34e 100644
--- a/models/spacer/src/main.rs
+++ b/models/spacer/src/main.rs
@@ -1,6 +1,4 @@
-use anyhow::Result;
 use clap::Parser;
-use fj::{Args, Instance};
 
 #[derive(Parser)]
 struct Parameters {
@@ -17,11 +15,11 @@ struct Parameters {
     height: f64,
 
     #[command(flatten)]
-    fj: Args,
+    fj: fj::Args,
 }
 
-fn main() -> Result<()> {
-    let mut fj = Instance::new();
+fn main() -> fj::Result {
+    let mut fj = fj::Instance::new();
     let params = Parameters::parse();
 
     let model = spacer::model(
diff --git a/models/star/Cargo.toml b/models/star/Cargo.toml
index c205fd4f7..738ef3b92 100644
--- a/models/star/Cargo.toml
+++ b/models/star/Cargo.toml
@@ -3,11 +3,6 @@ name = "star"
 version = "0.1.0"
 edition = "2021"
 
-[[bin]]
-name = "star"
-path = "src/main.rs"
-
 [dependencies]
 fj = { path = "../../crates/fj" }
 clap = { version = "4.5", features = ["derive"] }
-anyhow = "1.0"
diff --git a/models/star/src/main.rs b/models/star/src/main.rs
index d44ea64e1..eb6da2287 100644
--- a/models/star/src/main.rs
+++ b/models/star/src/main.rs
@@ -1,6 +1,4 @@
-use anyhow::Result;
 use clap::Parser;
-use fj::{Args, Instance};
 
 #[derive(Parser)]
 struct Parameters {
@@ -21,11 +19,11 @@ struct Parameters {
     height: f64,
 
     #[command(flatten)]
-    fj: Args,
+    fj: fj::Args,
 }
 
-fn main() -> Result<()> {
-    let mut fj = Instance::new();
+fn main() -> fj::Result {
+    let mut fj = fj::Instance::new();
     let params = Parameters::parse();
 
     let model = star::model(