diff --git a/cli/src/main.rs b/cli/src/main.rs
index 5463c3ecf..cdbd59263 100644
--- a/cli/src/main.rs
+++ b/cli/src/main.rs
@@ -641,8 +641,7 @@ impl FontSearcher {
         }
     }
 
-    /// Search for all fonts in a directory.
-    /// recursively.
+    /// Search for all fonts in a directory recursively.
     fn search_dir(&mut self, path: impl AsRef<Path>) {
         for entry in WalkDir::new(path)
             .follow_links(true)
diff --git a/library/src/layout/page.rs b/library/src/layout/page.rs
index 9d5d4f561..42db02c39 100644
--- a/library/src/layout/page.rs
+++ b/library/src/layout/page.rs
@@ -196,7 +196,7 @@ impl Cast<Spanned<Value>> for Marginal {
             Value::Str(v) => Ok(Self::Content(TextNode::packed(v))),
             Value::Content(v) => Ok(Self::Content(v)),
             Value::Func(v) => Ok(Self::Func(v, value.span)),
-            v => Err(format!(
+            v => Err(format_eco!(
                 "expected none, content or function, found {}",
                 v.type_name(),
             )),
diff --git a/library/src/structure/list.rs b/library/src/structure/list.rs
index 462e0c32e..6bfddd2e8 100644
--- a/library/src/structure/list.rs
+++ b/library/src/structure/list.rs
@@ -263,7 +263,7 @@ impl Cast<Spanned<Value>> for Label {
             Value::Str(v) => Ok(Self::Pattern(v.parse()?)),
             Value::Content(v) => Ok(Self::Content(v)),
             Value::Func(v) => Ok(Self::Func(v, value.span)),
-            v => Err(format!(
+            v => Err(format_eco!(
                 "expected string, content or function, found {}",
                 v.type_name(),
             )),
diff --git a/src/diag.rs b/src/diag.rs
index 58eebf8bc..29e43b918 100644
--- a/src/diag.rs
+++ b/src/diag.rs
@@ -154,13 +154,13 @@ impl<T> Trace<T> for SourceResult<T> {
 }
 
 /// A result type with a string error message.
-pub type StrResult<T> = Result<T, String>;
+pub type StrResult<T> = Result<T, EcoString>;
 
 /// Transform `expected X, found Y` into `expected X or A, found Y`.
-pub fn with_alternative(msg: String, alt: &str) -> String {
+pub fn with_alternative(msg: EcoString, alt: &str) -> EcoString {
     let mut parts = msg.split(", found ");
     if let (Some(a), Some(b)) = (parts.next(), parts.next()) {
-        format!("{} or {}, found {}", a, alt, b)
+        format_eco!("{} or {}, found {}", a, alt, b)
     } else {
         msg
     }
diff --git a/src/export/pdf/mod.rs b/src/export/pdf/mod.rs
index 7a530f041..7e5a3c064 100644
--- a/src/export/pdf/mod.rs
+++ b/src/export/pdf/mod.rs
@@ -21,10 +21,6 @@ use crate::image::Image;
 
 /// Export a document into a PDF file.
 ///
-/// This creates one page per frame. In addition to the frames, you need to pass
-/// in the context used during compilation so that fonts and images can be
-/// included in the PDF.
-///
 /// Returns the raw bytes making up the PDF file.
 pub fn pdf(document: &Document) -> Vec<u8> {
     let mut ctx = PdfContext::new(&document.metadata);
diff --git a/src/export/render.rs b/src/export/render.rs
index 14654b9b8..a61ff1be3 100644
--- a/src/export/render.rs
+++ b/src/export/render.rs
@@ -16,11 +16,8 @@ use crate::image::{DecodedImage, Image};
 
 /// Export a frame into a raster image.
 ///
-/// This renders the frame at the given number of pixels per printer's point and
-/// returns the resulting `tiny-skia` pixel buffer.
-///
-/// In addition to the frame, you need to pass in the context used during
-/// compilation so that fonts and images can be rendered.
+/// This renders the frame at the given number of pixels per point and returns
+/// the resulting `tiny-skia` pixel buffer.
 pub fn render(frame: &Frame, pixel_per_pt: f32) -> sk::Pixmap {
     let size = frame.size();
     let pxw = (pixel_per_pt * size.x.to_f32()).round().max(1.0) as u32;
diff --git a/src/model/array.rs b/src/model/array.rs
index 5a2f86729..06d1b5885 100644
--- a/src/model/array.rs
+++ b/src/model/array.rs
@@ -6,7 +6,7 @@ use std::sync::Arc;
 use super::{ops, Args, Func, Value, Vm};
 use crate::diag::{At, SourceResult, StrResult};
 use crate::syntax::Spanned;
-use crate::util::ArcExt;
+use crate::util::{format_eco, ArcExt, EcoString};
 
 /// Create a new [`Array`] from values.
 #[macro_export]
@@ -253,7 +253,7 @@ impl Array {
         vec.sort_by(|a, b| {
             a.partial_cmp(b).unwrap_or_else(|| {
                 if result.is_ok() {
-                    result = Err(format!(
+                    result = Err(format_eco!(
                         "cannot order {} and {}",
                         a.type_name(),
                         b.type_name(),
@@ -294,13 +294,13 @@ impl Array {
 
 /// The out of bounds access error message.
 #[cold]
-fn out_of_bounds(index: i64, len: i64) -> String {
-    format!("array index out of bounds (index: {}, len: {})", index, len)
+fn out_of_bounds(index: i64, len: i64) -> EcoString {
+    format_eco!("array index out of bounds (index: {}, len: {})", index, len)
 }
 
 /// The error message when the array is empty.
 #[cold]
-fn array_is_empty() -> String {
+fn array_is_empty() -> EcoString {
     "array is empty".into()
 }
 
diff --git a/src/model/cast.rs b/src/model/cast.rs
index a4a3fe4ec..df3c8c81d 100644
--- a/src/model/cast.rs
+++ b/src/model/cast.rs
@@ -9,7 +9,7 @@ use crate::geom::{
     Axes, Corners, Dir, GenAlign, Get, Length, Paint, PartialStroke, Point, Rel, Sides,
 };
 use crate::syntax::Spanned;
-use crate::util::EcoString;
+use crate::util::{format_eco, EcoString};
 
 /// Cast from a value to a specific type.
 pub trait Cast<V = Value>: Sized {
@@ -94,7 +94,11 @@ macro_rules! __castable {
                     v => v.type_name(),
                 };
 
-                Err(format!("expected {}, found {}", $expected, found))
+                Err($crate::util::format_eco!(
+                    "expected {}, found {}",
+                    $expected,
+                    found,
+                ))
             }
         }
     };
@@ -426,7 +430,7 @@ where
             };
 
             if let Some((key, _)) = dict.iter().next() {
-                return Err(format!("unexpected key {key:?}"));
+                return Err(format_eco!("unexpected key {key:?}"));
             }
 
             Ok(sides.map(Option::unwrap_or_default))
@@ -468,7 +472,7 @@ where
             };
 
             if let Some((key, _)) = dict.iter().next() {
-                return Err(format!("unexpected key {key:?}"));
+                return Err(format_eco!("unexpected key {key:?}"));
             }
 
             Ok(corners.map(Option::unwrap_or_default))
diff --git a/src/model/dict.rs b/src/model/dict.rs
index 1c2997958..d54a0e824 100644
--- a/src/model/dict.rs
+++ b/src/model/dict.rs
@@ -7,7 +7,7 @@ use super::{Args, Array, Func, Str, Value, Vm};
 use crate::diag::{SourceResult, StrResult};
 use crate::syntax::is_ident;
 use crate::syntax::Spanned;
-use crate::util::ArcExt;
+use crate::util::{format_eco, ArcExt, EcoString};
 
 /// Create a new [`Dict`] from key-value pairs.
 #[macro_export]
@@ -122,8 +122,8 @@ impl Dict {
 
 /// The missing key access error message.
 #[cold]
-fn missing_key(key: &str) -> String {
-    format!("dictionary does not contain key {:?}", Str::from(key))
+fn missing_key(key: &str) -> EcoString {
+    format_eco!("dictionary does not contain key {:?}", Str::from(key))
 }
 
 impl Debug for Dict {
diff --git a/src/model/ops.rs b/src/model/ops.rs
index 9a731d655..60b1c4498 100644
--- a/src/model/ops.rs
+++ b/src/model/ops.rs
@@ -3,13 +3,14 @@
 use super::{Regex, Smart, Value};
 use crate::diag::StrResult;
 use crate::geom::{Axes, Axis, GenAlign, Length, Numeric, PartialStroke, Rel};
+use crate::util::format_eco;
 use std::cmp::Ordering;
 use Value::*;
 
 /// Bail with a type mismatch error.
 macro_rules! mismatch {
     ($fmt:expr, $($value:expr),* $(,)?) => {
-        return Err(format!($fmt, $($value.type_name()),*))
+        return Err(format_eco!($fmt, $($value.type_name()),*))
     };
 }
 
@@ -104,7 +105,7 @@ pub fn add(lhs: Value, rhs: Value) -> StrResult<Value> {
                 (a.downcast::<GenAlign>(), b.downcast::<GenAlign>())
             {
                 if a.axis() == b.axis() {
-                    return Err(format!("cannot add two {:?} alignments", a.axis()));
+                    return Err(format_eco!("cannot add two {:?} alignments", a.axis()));
                 }
 
                 return Ok(Value::dynamic(match a.axis() {
diff --git a/src/model/str.rs b/src/model/str.rs
index 1fcf7075d..0c288d9b7 100644
--- a/src/model/str.rs
+++ b/src/model/str.rs
@@ -8,7 +8,7 @@ use unicode_segmentation::UnicodeSegmentation;
 use super::{castable, dict, Array, Dict, Value};
 use crate::diag::StrResult;
 use crate::geom::GenAlign;
-use crate::util::EcoString;
+use crate::util::{format_eco, EcoString};
 
 /// Create a new [`Str`] from a format string.
 #[macro_export]
@@ -401,7 +401,7 @@ pub struct Regex(regex::Regex);
 impl Regex {
     /// Create a new regular expression.
     pub fn new(re: &str) -> StrResult<Self> {
-        regex::Regex::new(re).map(Self).map_err(|err| err.to_string())
+        regex::Regex::new(re).map(Self).map_err(|err| format_eco!("{err}"))
     }
 }
 
diff --git a/src/model/value.rs b/src/model/value.rs
index 043fde343..59dac7201 100644
--- a/src/model/value.rs
+++ b/src/model/value.rs
@@ -344,7 +344,7 @@ macro_rules! primitive {
                 match value {
                     Value::$variant(v) => Ok(v),
                     $(Value::$other$(($binding))? => Ok($out),)*
-                    v => Err(format!(
+                    v => Err(format_eco!(
                         "expected {}, found {}",
                         Self::TYPE_NAME,
                         v.type_name(),