diff --git a/compiler/constrain/src/expr.rs b/compiler/constrain/src/expr.rs
index 51ca5b1cbc..cbce2021ce 100644
--- a/compiler/constrain/src/expr.rs
+++ b/compiler/constrain/src/expr.rs
@@ -718,7 +718,7 @@ pub fn constrain_expr(
                     Box::new(Type::Variable(*ext_var)),
                 ),
                 expected.clone(),
-                Category::TagUnion,
+                Category::TagApply(name.clone()),
                 region,
             );
             let ast_con = Eq(
diff --git a/compiler/constrain/src/uniq.rs b/compiler/constrain/src/uniq.rs
index 77cc1fc790..38bdf328ab 100644
--- a/compiler/constrain/src/uniq.rs
+++ b/compiler/constrain/src/uniq.rs
@@ -559,11 +559,16 @@ pub fn constrain_expr(
                 ),
             );
 
-            let union_con = Eq(union_type, expected.clone(), Category::TagUnion, region);
+            let union_con = Eq(
+                union_type,
+                expected.clone(),
+                Category::TagApply(name.clone()),
+                region,
+            );
             let ast_con = Eq(
                 Type::Variable(*variant_var),
                 expected,
-                Category::TagUnion,
+                Category::TagApply(name.clone()),
                 region,
             );
 
diff --git a/compiler/reporting/src/report.rs b/compiler/reporting/src/report.rs
index 7b8c853f16..9ecefc7ff8 100644
--- a/compiler/reporting/src/report.rs
+++ b/compiler/reporting/src/report.rs
@@ -174,6 +174,12 @@ pub enum ReportText {
     /// A global tag rendered as code (e.g. a monospace font, or with backticks around it).
     GlobalTag(Box<str>),
 
+    /// A private tag rendered as code (e.g. a monospace font, or with backticks around it).
+    PrivateTag(Symbol),
+
+    /// A record field name rendered as code (e.g. a monospace font, or with backticks around it).
+    RecordField(Box<str>),
+
     /// A language keyword like `if`, rendered as code (e.g. a monospace font, or with backticks around it).
     Keyword(Box<str>),
 
@@ -205,10 +211,18 @@ pub fn em_text(str: &str) -> ReportText {
     ReportText::EmText(Box::from(str))
 }
 
+pub fn private_tag_text(symbol: Symbol) -> ReportText {
+    ReportText::PrivateTag(symbol)
+}
+
 pub fn global_tag_text(str: &str) -> ReportText {
     ReportText::GlobalTag(Box::from(str))
 }
 
+pub fn record_field_text(str: &str) -> ReportText {
+    ReportText::RecordField(Box::from(str))
+}
+
 pub fn keyword_text(str: &str) -> ReportText {
     ReportText::Keyword(Box::from(str))
 }
@@ -323,12 +337,19 @@ impl ReportText {
                 buf.push_str(&string);
                 buf.push('`');
             }
+            RecordField(string) => {
+                // Since this is CI, the best we can do for code text is backticks.
+                buf.push('`');
+                buf.push('.');
+                buf.push_str(&string);
+                buf.push('`');
+            }
             Url(url) => {
                 buf.push('<');
                 buf.push_str(&url);
                 buf.push('>');
             }
-            Value(symbol) => {
+            PrivateTag(symbol) | Value(symbol) => {
                 if symbol.module_id() == env.home {
                     // Render it unqualified if it's in the current module.
                     buf.push_str(symbol.ident_string(env.interns));
diff --git a/compiler/reporting/src/type_error.rs b/compiler/reporting/src/type_error.rs
index e13d98e495..9f53f175b0 100644
--- a/compiler/reporting/src/type_error.rs
+++ b/compiler/reporting/src/type_error.rs
@@ -1,4 +1,7 @@
-use crate::report::{global_tag_text, keyword_text, plain_text, with_indent, Report, ReportText};
+use crate::report::{
+    global_tag_text, keyword_text, plain_text, private_tag_text, record_field_text, with_indent,
+    Report, ReportText,
+};
 use roc_can::expected::{Expected, PExpected};
 use roc_module::symbol::Symbol;
 use roc_solve::solve;
@@ -275,13 +278,72 @@ fn lone_type(
 }
 
 fn add_category(this_is: ReportText, category: &Category) -> ReportText {
+    use roc_module::ident::TagName;
     use Category::*;
     use ReportText::*;
 
     match category {
+        Lookup(name) => Concat(vec![
+            plain_text("This "),
+            Value(*name),
+            plain_text(" value is a"),
+        ]),
+
+        If => Concat(vec![
+            plain_text("This "),
+            keyword_text("if"),
+            plain_text("expression produces"),
+        ]),
+        When => Concat(vec![
+            plain_text("This "),
+            keyword_text("when"),
+            plain_text("expression produces"),
+        ]),
+
+        List => Concat(vec![this_is, plain_text("a list of type")]),
+        Num => Concat(vec![this_is, plain_text("a number of type")]),
+        Int => Concat(vec![this_is, plain_text("an integer of type")]),
+        Float => Concat(vec![this_is, plain_text("a float of type")]),
         Str => Concat(vec![this_is, plain_text(" a string of type")]),
+
+        Lambda => Concat(vec![this_is, plain_text("an anonymous function of type")]),
+
+        TagApply(TagName::Global(name)) => Concat(vec![
+            plain_text("This "),
+            global_tag_text(name.as_str()),
+            plain_text(" global tag application produces"),
+        ]),
+        TagApply(TagName::Private(name)) => Concat(vec![
+            plain_text("This "),
+            private_tag_text(*name),
+            plain_text(" private tag application produces"),
+        ]),
+
+        Record => Concat(vec![this_is, plain_text("a record of type")]),
+
+        Accessor(field) => Concat(vec![
+            plain_text("This "),
+            record_field_text(field.as_str()),
+            plain_text(" value is a"),
+        ]),
+        Access(field) => Concat(vec![
+            plain_text("The value at "),
+            record_field_text(field.as_str()),
+            plain_text(" is a"),
+        ]),
+
+        CallResult(Some(symbol)) => Concat(vec![
+            plain_text("This "),
+            Value(*symbol),
+            plain_text(" call produces"),
+        ]),
+        CallResult(None) => Concat(vec![this_is]),
+
+        Uniqueness => Concat(vec![
+            this_is,
+            plain_text(" an uniqueness attribute of type"),
+        ]),
         Storage => Concat(vec![this_is, plain_text(" a value of type")]),
-        other => todo!("add_category for {:?}", other),
     }
 }
 
diff --git a/compiler/types/src/types.rs b/compiler/types/src/types.rs
index 36bd30178e..3ee5bad08c 100644
--- a/compiler/types/src/types.rs
+++ b/compiler/types/src/types.rs
@@ -637,6 +637,7 @@ pub enum Reason {
 pub enum Category {
     Lookup(Symbol),
     CallResult(Option<Symbol>),
+    TagApply(TagName),
     Lambda,
     Uniqueness,
 
@@ -651,7 +652,6 @@ pub enum Category {
     Float,
     Int,
     Num,
-    TagUnion,
     List,
     Str,