diff --git a/tools/src/recipe.rs b/tools/src/recipe.rs
index 2796788..5961cdb 100644
--- a/tools/src/recipe.rs
+++ b/tools/src/recipe.rs
@@ -6,7 +6,7 @@ pub enum Unit {
 }
 
 /// `Quantity` measures the amount of a resource (Input or Output).
-#[derive(Clone, Copy, serde::Deserialize)]
+#[derive(Clone, Copy, PartialEq, serde::Deserialize)]
 pub struct Quantity {
     pub amount: f32,
     pub unit: Option<Unit>,
@@ -37,7 +37,7 @@ pub struct Input {
     pub quantity: Quantity,
 }
 
-#[derive(Debug, serde::Deserialize)]
+#[derive(Debug, PartialEq, serde::Deserialize)]
 pub struct Output {
     // Quantity defaults to "amount=1" if omitted.
     #[serde(default)]
@@ -91,7 +91,18 @@ pub struct Recipe {
 impl Recipe {
     pub fn from_file(file: &std::path::PathBuf) -> anyhow::Result<Self> {
         let recipe_contents = std::fs::read_to_string(file)?;
-        let recipe: Recipe = toml::from_str(&recipe_contents)?;
+        let mut recipe: Recipe = toml::from_str(&recipe_contents)?;
+        if recipe.outputs == None {
+            if let Some(recipe_name) = file.file_stem() {
+                let mut outputs = std::collections::HashMap::<String, Output>::new();
+                let key = recipe_name.to_string_lossy().into_owned();
+                let value = Output {
+                    quantity: Quantity::default(),
+                };
+                outputs.insert(key, value);
+                recipe.outputs = Some(outputs);
+            }
+        }
         // let r = recipe.validate_recipe();
         Ok(recipe)
     }
diff --git a/tools/src/repo.rs b/tools/src/repo.rs
index c5eb6a8..dfd4f9a 100644
--- a/tools/src/repo.rs
+++ b/tools/src/repo.rs
@@ -79,7 +79,15 @@ impl Repo {
         // println!("reading Recipe from {:?}", path);
         if let Some(recipe_name) = path.file_stem() {
             let key = recipe_name.to_string_lossy().into_owned();
-            let value = crate::Recipe::from_file(path)?;
+            let value = match crate::Recipe::from_file(path) {
+                Ok(recipe) => recipe,
+                Err(e) => {
+                    return Err(anyhow::Error::msg(format!(
+                        "failed to read recipe {}: {:?}",
+                        key, e
+                    )));
+                }
+            };
             self.recipes.insert(key, value);
         }
         Ok(())
@@ -93,7 +101,15 @@ impl Repo {
         indent: usize,
     ) -> anyhow::Result<()> {
         for (input_name, input_info) in recipe.inputs.iter() {
-            let input_recipe = self.get_recipe(input_name).unwrap();
+            let input_recipe = match self.get_recipe(input_name) {
+                Some(recipe) => recipe,
+                None => {
+                    return Err(anyhow::Error::msg(format!(
+                        "failed to get recipe '{}'",
+                        input_name
+                    )));
+                }
+            };
 
             // A Recipe whose only input is Capital is a Vitamin.
             let cost = match input_recipe.is_vitamin() {
@@ -109,10 +125,12 @@ impl Repo {
                             .ok_or(anyhow::Error::msg(format!(
                                 "can't find input capital for {input_name}"
                             )))?;
-                    assert_eq!(
-                        input_capital.quantity.unit,
-                        Some(crate::recipe::Unit::USDollar)
-                    );
+                    if input_capital.quantity.unit != Some(crate::recipe::Unit::USDollar) {
+                        return Err(anyhow::Error::msg(format!(
+                            "{} input capital does not have units USDollar",
+                            input_name
+                        )));
+                    }
                     let cost = input_capital.quantity.amount;
 
                     let outputs = match &input_recipe.outputs {