diff --git a/docs/docs/snippets/supported-types.mdx b/docs/docs/snippets/supported-types.mdx
index 2f8456fce..d19bfebf0 100644
--- a/docs/docs/snippets/supported-types.mdx
+++ b/docs/docs/snippets/supported-types.mdx
@@ -217,12 +217,12 @@ A mapping of strings to elements of another type.
 
 **Example**: `map<string, string>`
 
-<Info>
+{/* <Info>
   For TS users: `map<string, ValueType>` will generate a 
   `Record<string, ValueType>` type annotation, but using any other type for the
   key will generate a `Map`, e.g. `map<int, string>` in BAML will generate a
   `Map<number, string>` type annotation in TypeScript.
-</Info>
+</Info> */}
 
 ### ❌ Set
 
diff --git a/engine/baml-lib/baml-core/src/ir/ir_helpers/to_baml_arg.rs b/engine/baml-lib/baml-core/src/ir/ir_helpers/to_baml_arg.rs
index bc487e8b1..bb48d0dae 100644
--- a/engine/baml-lib/baml-core/src/ir/ir_helpers/to_baml_arg.rs
+++ b/engine/baml-lib/baml-core/src/ir/ir_helpers/to_baml_arg.rs
@@ -1,7 +1,5 @@
 use baml_types::{BamlMap, BamlMediaType, BamlValue, FieldType, TypeValue};
 use core::result::Result;
-use log::kv;
-use std::ops::Deref;
 
 use crate::ir::IntermediateRepr;
 
@@ -68,7 +66,7 @@ pub fn validate_arg(
                             .and_then(|v| v.as_str())
                             .unwrap_or_default()
                             .to_string();
-                        Some(BamlValue::Media(baml_types::BamlMedia::url(
+                        Ok(BamlValue::Media(baml_types::BamlMedia::url(
                             BamlMediaType::Image,
                             s.to_string(),
                             Some(media_type_str),
@@ -79,7 +77,7 @@ pub fn validate_arg(
                             .and_then(|v| v.as_str())
                             .unwrap_or_default()
                             .to_string();
-                        Some(BamlValue::Media(baml_types::BamlMedia::base64(
+                        Ok(BamlValue::Media(baml_types::BamlMedia::base64(
                             BamlMediaType::Image,
                             s.to_string(),
                             media_type_str,
@@ -106,7 +104,7 @@ pub fn validate_arg(
                             .and_then(|v| v.as_str())
                             .unwrap_or_default()
                             .to_string();
-                        Some(BamlValue::Media(baml_types::BamlMedia::url(
+                        Ok(BamlValue::Media(baml_types::BamlMedia::url(
                             BamlMediaType::Audio,
                             s.to_string(),
                             Some(media_type_str),
@@ -117,7 +115,7 @@ pub fn validate_arg(
                             .and_then(|v| v.as_str())
                             .unwrap_or_default()
                             .to_string();
-                        Some(BamlValue::Media(baml_types::BamlMedia::base64(
+                        Ok(BamlValue::Media(baml_types::BamlMedia::base64(
                             BamlMediaType::Audio,
                             s.to_string(),
                             media_type_str,
diff --git a/engine/baml-lib/baml-core/src/validate/validation_pipeline/validations.rs b/engine/baml-lib/baml-core/src/validate/validation_pipeline/validations.rs
index e18bf6621..df3a3da89 100644
--- a/engine/baml-lib/baml-core/src/validate/validation_pipeline/validations.rs
+++ b/engine/baml-lib/baml-core/src/validate/validation_pipeline/validations.rs
@@ -1,10 +1,10 @@
 mod classes;
 mod clients;
-mod common;
 mod configurations;
 mod cycle;
 mod enums;
 mod functions;
+mod types;
 mod variants;
 
 use super::context::Context;
diff --git a/engine/baml-lib/baml-core/src/validate/validation_pipeline/validations/classes.rs b/engine/baml-lib/baml-core/src/validate/validation_pipeline/validations/classes.rs
index ef9370875..946963d63 100644
--- a/engine/baml-lib/baml-core/src/validate/validation_pipeline/validations/classes.rs
+++ b/engine/baml-lib/baml-core/src/validate/validation_pipeline/validations/classes.rs
@@ -1,6 +1,6 @@
 use crate::validate::validation_pipeline::context::Context;
 
-use super::common::validate_type_exists;
+use super::types::validate_type;
 
 pub(super) fn validate(ctx: &mut Context<'_>) {
     for cls in ctx.db.walk_classes() {
@@ -8,11 +8,11 @@ pub(super) fn validate(ctx: &mut Context<'_>) {
 
         for c in cls.static_fields() {
             let field = c.ast_field();
-            validate_type_exists(ctx, &field.field_type);
+            validate_type(ctx, &field.field_type);
         }
         for c in cls.dynamic_fields() {
             let field = c.ast_field();
-            validate_type_exists(ctx, &field.field_type);
+            validate_type(ctx, &field.field_type);
         }
     }
 }
diff --git a/engine/baml-lib/baml-core/src/validate/validation_pipeline/validations/common.rs b/engine/baml-lib/baml-core/src/validate/validation_pipeline/validations/common.rs
deleted file mode 100644
index 1c41220fa..000000000
--- a/engine/baml-lib/baml-core/src/validate/validation_pipeline/validations/common.rs
+++ /dev/null
@@ -1,26 +0,0 @@
-use internal_baml_diagnostics::DatamodelError;
-use internal_baml_schema_ast::ast::{FieldType, Identifier, WithName, WithSpan};
-
-use crate::validate::validation_pipeline::context::Context;
-
-fn errors_with_names<'a>(ctx: &'a mut Context<'_>, idn: &Identifier) {
-    // Push the error with the appropriate message
-    ctx.push_error(DatamodelError::new_type_not_found_error(
-        idn.name(),
-        ctx.db.valid_type_names(),
-        idn.span().clone(),
-    ));
-}
-
-pub(crate) fn validate_type_exists(ctx: &mut Context<'_>, field_type: &FieldType) {
-    field_type
-        .flat_idns()
-        .iter()
-        .for_each(|f| match ctx.db.find_type(f) {
-            Some(_) => {}
-            None => match f {
-                Identifier::Primitive(..) => {}
-                _ => errors_with_names(ctx, f),
-            },
-        });
-}
diff --git a/engine/baml-lib/baml-core/src/validate/validation_pipeline/validations/functions.rs b/engine/baml-lib/baml-core/src/validate/validation_pipeline/validations/functions.rs
index e066a479f..649b6d60f 100644
--- a/engine/baml-lib/baml-core/src/validate/validation_pipeline/validations/functions.rs
+++ b/engine/baml-lib/baml-core/src/validate/validation_pipeline/validations/functions.rs
@@ -3,13 +3,13 @@ use internal_baml_schema_ast::ast::{WithIdentifier, WithName, WithSpan};
 
 use crate::validate::validation_pipeline::context::Context;
 
-use super::common::validate_type_exists;
+use super::types::validate_type;
 
 pub(super) fn validate(ctx: &mut Context<'_>) {
     for func in ctx.db.walk_old_functions() {
         for args in func.walk_input_args().chain(func.walk_output_args()) {
             let arg = args.ast_arg();
-            validate_type_exists(ctx, &arg.1.field_type)
+            validate_type(ctx, &arg.1.field_type)
         }
 
         // Check if the function has multiple impls, if it does,
@@ -114,7 +114,7 @@ pub(super) fn validate(ctx: &mut Context<'_>) {
     for func in ctx.db.walk_new_functions() {
         for args in func.walk_input_args().chain(func.walk_output_args()) {
             let arg = args.ast_arg();
-            validate_type_exists(ctx, &arg.1.field_type)
+            validate_type(ctx, &arg.1.field_type)
         }
 
         // Ensure the client is correct.
diff --git a/engine/baml-lib/baml-core/src/validate/validation_pipeline/validations/types.rs b/engine/baml-lib/baml-core/src/validate/validation_pipeline/validations/types.rs
new file mode 100644
index 000000000..42754a94b
--- /dev/null
+++ b/engine/baml-lib/baml-core/src/validate/validation_pipeline/validations/types.rs
@@ -0,0 +1,66 @@
+use baml_types::TypeValue;
+use internal_baml_diagnostics::DatamodelError;
+use internal_baml_schema_ast::ast::{FieldArity, FieldType, Identifier, WithName, WithSpan};
+
+use crate::validate::validation_pipeline::context::Context;
+
+fn errors_with_names<'a>(ctx: &'a mut Context<'_>, idn: &Identifier) {
+    // Push the error with the appropriate message
+    ctx.push_error(DatamodelError::new_type_not_found_error(
+        idn.name(),
+        ctx.db.valid_type_names(),
+        idn.span().clone(),
+    ));
+}
+
+/// Called for each type in the baml_src tree, validates that it is well-formed.
+///
+/// Operates in two passes:
+///
+///   1. Verify that the type is resolveable (for REF types)
+///   2. Verify that the type is well-formed/allowed in the language
+pub(crate) fn validate_type(ctx: &mut Context<'_>, field_type: &FieldType) {
+    validate_type_exists(ctx, field_type);
+    validate_type_allowed(ctx, field_type);
+}
+
+fn validate_type_exists(ctx: &mut Context<'_>, field_type: &FieldType) {
+    field_type
+        .flat_idns()
+        .iter()
+        .for_each(|f| match ctx.db.find_type(f) {
+            Some(_) => {}
+            None => match f {
+                Identifier::Primitive(..) => {}
+                _ => errors_with_names(ctx, f),
+            },
+        });
+}
+
+fn validate_type_allowed(ctx: &mut Context<'_>, field_type: &FieldType) {
+    match field_type {
+        FieldType::Map(kv_types, _) => {
+            match &kv_types.0 {
+                FieldType::Identifier(
+                    FieldArity::Required,
+                    Identifier::Primitive(TypeValue::String, _),
+                ) => {}
+                key_type => {
+                    ctx.push_error(DatamodelError::new_validation_error(
+                        "Maps may only have strings as keys",
+                        key_type.span().clone(),
+                    ));
+                }
+            }
+            validate_type_allowed(ctx, &kv_types.1);
+            // TODO:assert key_type is string or int or null
+        }
+        FieldType::Identifier(_, _) => {}
+        FieldType::List(field_type, _, _) => validate_type_allowed(ctx, field_type),
+        FieldType::Tuple(_, field_types, _) | FieldType::Union(_, field_types, _) => {
+            for field_type in field_types {
+                validate_type_allowed(ctx, field_type);
+            }
+        }
+    }
+}
diff --git a/engine/baml-lib/baml/tests/validation_files/class/map_types.baml b/engine/baml-lib/baml/tests/validation_files/class/map_types.baml
index be9c63e61..da3597ad0 100644
--- a/engine/baml-lib/baml/tests/validation_files/class/map_types.baml
+++ b/engine/baml-lib/baml/tests/validation_files/class/map_types.baml
@@ -7,52 +7,58 @@ class MapDummy {
 class MapFields {
   a1 map<string, string>
   a2 map<string, int>
-  a2 map<string, MapDummy>
+  a3 map<string, MapDummy>
 
   b1 map<int, string>
   b2 map<float, string>
   b3 map<MapDummy, string>
+  b4 map<string?, string>
+  b5 map<string | int, string>
+
+  c1 string | map<string, string>
+  c2 string | map<int, string>
+  c3 string | map<string?, string>
 }
 
-// error: Error validating: This line is not a valid field or attribute definition. A valid class property looks like: 'myProperty string[] @description("This is a description")'
-//   -->  class/map_types.baml:8
-//    | 
-//  7 | class MapFields {
-//  8 |   a1 map<string, string>
-//  9 |   a2 map<string, int>
-//    | 
-// error: Error validating: This line is not a valid field or attribute definition. A valid class property looks like: 'myProperty string[] @description("This is a description")'
-//   -->  class/map_types.baml:9
-//    | 
-//  8 |   a1 map<string, string>
-//  9 |   a2 map<string, int>
-// 10 |   a2 map<string, MapDummy>
-//    | 
-// error: Error validating: This line is not a valid field or attribute definition. A valid class property looks like: 'myProperty string[] @description("This is a description")'
-//   -->  class/map_types.baml:10
-//    | 
-//  9 |   a2 map<string, int>
-// 10 |   a2 map<string, MapDummy>
-// 11 | 
-//    | 
-// error: Error validating: This line is not a valid field or attribute definition. A valid class property looks like: 'myProperty string[] @description("This is a description")'
+// error: Error validating: Maps may only have strings as keys
 //   -->  class/map_types.baml:12
 //    | 
 // 11 | 
 // 12 |   b1 map<int, string>
-// 13 |   b2 map<float, string>
 //    | 
-// error: Error validating: This line is not a valid field or attribute definition. A valid class property looks like: 'myProperty string[] @description("This is a description")'
+// error: Error validating: Maps may only have strings as keys
 //   -->  class/map_types.baml:13
 //    | 
 // 12 |   b1 map<int, string>
 // 13 |   b2 map<float, string>
-// 14 |   b3 map<MapDummy, string>
 //    | 
-// error: Error validating: This line is not a valid field or attribute definition. A valid class property looks like: 'myProperty string[] @description("This is a description")'
+// error: Error validating: Maps may only have strings as keys
 //   -->  class/map_types.baml:14
 //    | 
 // 13 |   b2 map<float, string>
 // 14 |   b3 map<MapDummy, string>
-// 15 | }
+//    | 
+// error: Error validating: Maps may only have strings as keys
+//   -->  class/map_types.baml:15
+//    | 
+// 14 |   b3 map<MapDummy, string>
+// 15 |   b4 map<string?, string>
+//    | 
+// error: Error validating: Maps may only have strings as keys
+//   -->  class/map_types.baml:16
+//    | 
+// 15 |   b4 map<string?, string>
+// 16 |   b5 map<string | int, string>
+//    | 
+// error: Error validating: Maps may only have strings as keys
+//   -->  class/map_types.baml:19
+//    | 
+// 18 |   c1 string | map<string, string>
+// 19 |   c2 string | map<int, string>
+//    | 
+// error: Error validating: Maps may only have strings as keys
+//   -->  class/map_types.baml:20
+//    | 
+// 19 |   c2 string | map<int, string>
+// 20 |   c3 string | map<string?, string>
 //    | 
diff --git a/engine/baml-lib/baml/tests/validation_files/class/secure_types.baml b/engine/baml-lib/baml/tests/validation_files/class/secure_types.baml
index 8c1885e90..1f1886770 100644
--- a/engine/baml-lib/baml/tests/validation_files/class/secure_types.baml
+++ b/engine/baml-lib/baml/tests/validation_files/class/secure_types.baml
@@ -17,207 +17,45 @@ class ComplexTypes {
   o (((int | string) | bool[]), (float, double) | long_long_identifier_123)
 }
 
-// error: Type `apple_pie` does not exist. Did you mean one of these: `ComplexTypes`, `float`, `bool`, `string`, `int`?
+// error: Error validating: This line is not a valid field or attribute definition. A valid class property looks like: 'myProperty string[] @description("This is a description")'
 //   -->  class/secure_types.baml:3
 //    | 
 //  2 | class ComplexTypes {
 //  3 |   a {string[]: (int | bool[]) | apple_pie[][]}
-//    | 
-// error: Type `char` does not exist. Did you mean one of these: `int`, `float`, `bool`, `string`, `ComplexTypes`?
-//   -->  class/secure_types.baml:4
-//    | 
-//  3 |   a {string[]: (int | bool[]) | apple_pie[][]}
 //  4 |   b (int, {bool: string?}, (char | float)[][] | long_word_123.foobar[])
 //    | 
-// error: Type `long_word_123.foobar` does not exist. Did you mean one of these: `float`, `bool`, `ComplexTypes`, `string`, `int`?
+// error: Error validating: This line is not a valid field or attribute definition. A valid class property looks like: 'myProperty string[] @description("This is a description")'
 //   -->  class/secure_types.baml:4
 //    | 
 //  3 |   a {string[]: (int | bool[]) | apple_pie[][]}
 //  4 |   b (int, {bool: string?}, (char | float)[][] | long_word_123.foobar[])
-//    | 
-// error: Type `apple123_456_pie` does not exist. Did you mean one of these: `ComplexTypes`, `float`, `bool`, `string`, `int`?
-//   -->  class/secure_types.baml:5
-//    | 
-//  4 |   b (int, {bool: string?}, (char | float)[][] | long_word_123.foobar[])
 //  5 |   c apple123_456_pie | (stringer, bool[], (int | char))[]
 //    | 
-// error: Type `stringer` does not exist. Did you mean one of these: `string`, `int`, `float`, `bool`, `ComplexTypes`?
-//   -->  class/secure_types.baml:5
-//    | 
-//  4 |   b (int, {bool: string?}, (char | float)[][] | long_word_123.foobar[])
-//  5 |   c apple123_456_pie | (stringer, bool[], (int | char))[]
-//    | 
-// error: Type `char` does not exist. Did you mean one of these: `int`, `float`, `bool`, `string`, `ComplexTypes`?
-//   -->  class/secure_types.baml:5
-//    | 
-//  4 |   b (int, {bool: string?}, (char | float)[][] | long_word_123.foobar[])
-//  5 |   c apple123_456_pie | (stringer, bool[], (int | char))[]
-//    | 
-// error: Type `char` does not exist. Did you mean one of these: `int`, `float`, `bool`, `string`, `ComplexTypes`?
+// error: Error validating: This line is not a valid field or attribute definition. A valid class property looks like: 'myProperty string[] @description("This is a description")'
 //   -->  class/secure_types.baml:6
 //    | 
 //  5 |   c apple123_456_pie | (stringer, bool[], (int | char))[]
 //  6 |   d {int[][]: ((int | float) | char[])}
-//    | 
-// error: Type `char` does not exist. Did you mean one of these: `int`, `float`, `bool`, `string`, `ComplexTypes`?
-//   -->  class/secure_types.baml:7
-//    | 
-//  6 |   d {int[][]: ((int | float) | char[])}
 //  7 |   e ((int, string | char) | ((float, double) | long[], bool)[][][])
 //    | 
-// error: Type `double` does not exist. Did you mean one of these: `bool`, `string`, `int`, `float`, `ComplexTypes`?
-//   -->  class/secure_types.baml:7
-//    | 
-//  6 |   d {int[][]: ((int | float) | char[])}
-//  7 |   e ((int, string | char) | ((float, double) | long[], bool)[][][])
-//    | 
-// error: Type `long` does not exist. Did you mean one of these: `int`, `float`, `bool`, `string`, `ComplexTypes`?
-//   -->  class/secure_types.baml:7
-//    | 
-//  6 |   d {int[][]: ((int | float) | char[])}
-//  7 |   e ((int, string | char) | ((float, double) | long[], bool)[][][])
-//    | 
-// error: Type `VeryLongWord_With_123_Numbers` does not exist.
-//   -->  class/secure_types.baml:8
-//    | 
-//  7 |   e ((int, string | char) | ((float, double) | long[], bool)[][][])
-//  8 |   f VeryLongWord_With_123_Numbers[][][][]
-//    | 
-// error: Type `char` does not exist. Did you mean one of these: `int`, `float`, `bool`, `string`, `ComplexTypes`?
-//   -->  class/secure_types.baml:9
-//    | 
-//  8 |   f VeryLongWord_With_123_Numbers[][][][]
-//  9 |   g (int, (float, char, bool), string[]) | tuple_inside_tuple[]
-//    | 
-// error: Type `tuple_inside_tuple` does not exist. Did you mean one of these: `ComplexTypes`, `int`, `string`, `float`, `bool`?
-//   -->  class/secure_types.baml:9
-//    | 
-//  8 |   f VeryLongWord_With_123_Numbers[][][][]
-//  9 |   g (int, (float, char, bool), string[]) | tuple_inside_tuple[]
-//    | 
-// error: Type `char` does not exist. Did you mean one of these: `int`, `float`, `bool`, `string`, `ComplexTypes`?
+// error: Error validating: This line is not a valid field or attribute definition. A valid class property looks like: 'myProperty string[] @description("This is a description")'
 //   -->  class/secure_types.baml:10
 //    | 
 //  9 |   g (int, (float, char, bool), string[]) | tuple_inside_tuple[]
 // 10 |   h (((int | string)[]) | {bool[][]: char[]})
-//    | 
-// error: Type `apple` does not exist. Did you mean one of these: `bool`, `int`, `float`, `string`, `ComplexTypes`?
-//   -->  class/secure_types.baml:11
-//    | 
-// 10 |   h (((int | string)[]) | {bool[][]: char[]})
-// 11 |   i (apple, banana | cherry | date_fruit | eggplant_vegetable)[]
-//    | 
-// error: Type `banana` does not exist. Did you mean one of these: `string`, `int`, `float`, `bool`, `ComplexTypes`?
-//   -->  class/secure_types.baml:11
-//    | 
-// 10 |   h (((int | string)[]) | {bool[][]: char[]})
-// 11 |   i (apple, banana | cherry | date_fruit | eggplant_vegetable)[]
-//    | 
-// error: Type `cherry` does not exist. Did you mean one of these: `string`, `int`, `float`, `bool`, `ComplexTypes`?
-//   -->  class/secure_types.baml:11
-//    | 
-// 10 |   h (((int | string)[]) | {bool[][]: char[]})
-// 11 |   i (apple, banana | cherry | date_fruit | eggplant_vegetable)[]
-//    | 
-// error: Type `date_fruit` does not exist. Did you mean one of these: `string`, `float`, `int`, `bool`, `ComplexTypes`?
-//   -->  class/secure_types.baml:11
-//    | 
-// 10 |   h (((int | string)[]) | {bool[][]: char[]})
-// 11 |   i (apple, banana | cherry | date_fruit | eggplant_vegetable)[]
-//    | 
-// error: Type `eggplant_vegetable` does not exist. Did you mean one of these: `ComplexTypes`, `string`, `int`, `float`, `bool`?
-//   -->  class/secure_types.baml:11
-//    | 
-// 10 |   h (((int | string)[]) | {bool[][]: char[]})
-// 11 |   i (apple, banana | cherry | date_fruit | eggplant_vegetable)[]
-//    | 
-// error: Type `char` does not exist. Did you mean one of these: `int`, `float`, `bool`, `string`, `ComplexTypes`?
-//   -->  class/secure_types.baml:12
-//    | 
-// 11 |   i (apple, banana | cherry | date_fruit | eggplant_vegetable)[]
-// 12 |   j ((char, int[][], (bool | string[][])) | double[][][][], (float, int)[])
-//    | 
-// error: Type `double` does not exist. Did you mean one of these: `bool`, `string`, `int`, `float`, `ComplexTypes`?
-//   -->  class/secure_types.baml:12
-//    | 
 // 11 |   i (apple, banana | cherry | date_fruit | eggplant_vegetable)[]
-// 12 |   j ((char, int[][], (bool | string[][])) | double[][][][], (float, int)[])
-//    | 
-// error: Type `long` does not exist. Did you mean one of these: `int`, `float`, `bool`, `string`, `ComplexTypes`?
-//   -->  class/secure_types.baml:13
-//    | 
-// 12 |   j ((char, int[][], (bool | string[][])) | double[][][][], (float, int)[])
-// 13 |   k {string[]: (int | long[])} | {float[][]: double[][]}
 //    | 
-// error: Type `double` does not exist. Did you mean one of these: `bool`, `string`, `int`, `float`, `ComplexTypes`?
+// error: Error validating: This line is not a valid field or attribute definition. A valid class property looks like: 'myProperty string[] @description("This is a description")'
 //   -->  class/secure_types.baml:13
 //    | 
 // 12 |   j ((char, int[][], (bool | string[][])) | double[][][][], (float, int)[])
 // 13 |   k {string[]: (int | long[])} | {float[][]: double[][]}
-//    | 
-// error: Type `AlphaNumeric_123_456_789` does not exist.
-//   -->  class/secure_types.baml:14
-//    | 
-// 13 |   k {string[]: (int | long[])} | {float[][]: double[][]}
-// 14 |   l AlphaNumeric_123_456_789 | (int, bool?) | char[]
-//    | 
-// error: Type `char` does not exist. Did you mean one of these: `int`, `float`, `bool`, `string`, `ComplexTypes`?
-//   -->  class/secure_types.baml:14
-//    | 
-// 13 |   k {string[]: (int | long[])} | {float[][]: double[][]}
 // 14 |   l AlphaNumeric_123_456_789 | (int, bool?) | char[]
 //    | 
-// error: Type `tuple_1` does not exist. Did you mean one of these: `float`, `bool`, `string`, `int`, `ComplexTypes`?
-//   -->  class/secure_types.baml:15
-//    | 
-// 14 |   l AlphaNumeric_123_456_789 | (int, bool?) | char[]
-// 15 |   m (tuple_1, tuple_2 | tuple_3, (tuple_4, tuple_5))[]
-//    | 
-// error: Type `tuple_2` does not exist. Did you mean one of these: `float`, `bool`, `string`, `int`, `ComplexTypes`?
-//   -->  class/secure_types.baml:15
-//    | 
-// 14 |   l AlphaNumeric_123_456_789 | (int, bool?) | char[]
-// 15 |   m (tuple_1, tuple_2 | tuple_3, (tuple_4, tuple_5))[]
-//    | 
-// error: Type `tuple_3` does not exist. Did you mean one of these: `float`, `bool`, `string`, `int`, `ComplexTypes`?
-//   -->  class/secure_types.baml:15
-//    | 
-// 14 |   l AlphaNumeric_123_456_789 | (int, bool?) | char[]
-// 15 |   m (tuple_1, tuple_2 | tuple_3, (tuple_4, tuple_5))[]
-//    | 
-// error: Type `tuple_4` does not exist. Did you mean one of these: `float`, `bool`, `string`, `int`, `ComplexTypes`?
-//   -->  class/secure_types.baml:15
-//    | 
-// 14 |   l AlphaNumeric_123_456_789 | (int, bool?) | char[]
-// 15 |   m (tuple_1, tuple_2 | tuple_3, (tuple_4, tuple_5))[]
-//    | 
-// error: Type `tuple_5` does not exist. Did you mean one of these: `float`, `bool`, `string`, `int`, `ComplexTypes`?
-//   -->  class/secure_types.baml:15
-//    | 
-// 14 |   l AlphaNumeric_123_456_789 | (int, bool?) | char[]
-// 15 |   m (tuple_1, tuple_2 | tuple_3, (tuple_4, tuple_5))[]
-//    | 
-// error: Type `another_key` does not exist. Did you mean one of these: `string`, `int`, `ComplexTypes`, `float`, `bool`?
+// error: Error validating: This line is not a valid field or attribute definition. A valid class property looks like: 'myProperty string[] @description("This is a description")'
 //   -->  class/secure_types.baml:16
 //    | 
 // 15 |   m (tuple_1, tuple_2 | tuple_3, (tuple_4, tuple_5))[]
 // 16 |   n {complex_key_type[]: {another_key: (int | string[])}}
-//    | 
-// error: Type `complex_key_type` does not exist. Did you mean one of these: `ComplexTypes`, `float`, `bool`, `int`, `string`?
-//   -->  class/secure_types.baml:16
-//    | 
-// 15 |   m (tuple_1, tuple_2 | tuple_3, (tuple_4, tuple_5))[]
-// 16 |   n {complex_key_type[]: {another_key: (int | string[])}}
-//    | 
-// error: Type `double` does not exist. Did you mean one of these: `bool`, `string`, `int`, `float`, `ComplexTypes`?
-//   -->  class/secure_types.baml:17
-//    | 
-// 16 |   n {complex_key_type[]: {another_key: (int | string[])}}
-// 17 |   o (((int | string) | bool[]), (float, double) | long_long_identifier_123)
-//    | 
-// error: Type `long_long_identifier_123` does not exist. Did you mean `ComplexTypes`?
-//   -->  class/secure_types.baml:17
-//    | 
-// 16 |   n {complex_key_type[]: {another_key: (int | string[])}}
 // 17 |   o (((int | string) | bool[]), (float, double) | long_long_identifier_123)
 //    | 
diff --git a/engine/baml-lib/jsonish/src/deserializer/coercer/coerce_array.rs b/engine/baml-lib/jsonish/src/deserializer/coercer/coerce_array.rs
index 0c96ea380..d22496147 100644
--- a/engine/baml-lib/jsonish/src/deserializer/coercer/coerce_array.rs
+++ b/engine/baml-lib/jsonish/src/deserializer/coercer/coerce_array.rs
@@ -35,7 +35,7 @@ pub(super) fn coerce_array(
             for (i, item) in arr.iter().enumerate() {
                 match inner.coerce(&ctx.enter_scope(&format!("{i}")), inner, Some(item)) {
                     Ok(v) => items.push(v),
-                    // TODO(vbv): this seems like a bug - it causes more penalization the deeper into an array it is?
+                    // TODO(vbv): document why we penalize in proportion to how deep into an array a parse error is
                     Err(e) => flags.add_flag(Flag::ArrayItemParseError(i, e)),
                 }
             }
diff --git a/engine/baml-lib/jsonish/src/tests/mod.rs b/engine/baml-lib/jsonish/src/tests/mod.rs
index 90835441f..99010f4af 100644
--- a/engine/baml-lib/jsonish/src/tests/mod.rs
+++ b/engine/baml-lib/jsonish/src/tests/mod.rs
@@ -8,6 +8,7 @@ mod test_basics;
 mod test_class;
 mod test_enum;
 mod test_lists;
+mod test_maps;
 mod test_partials;
 mod test_unions;
 
diff --git a/engine/baml-lib/jsonish/src/tests/test_lists.rs b/engine/baml-lib/jsonish/src/tests/test_lists.rs
index a51451997..4b7a56a36 100644
--- a/engine/baml-lib/jsonish/src/tests/test_lists.rs
+++ b/engine/baml-lib/jsonish/src/tests/test_lists.rs
@@ -38,7 +38,7 @@ test_deserializer!(
     class Foo {
         a int
         b string
-        }"#,
+    }"#,
     r#"[{"a": 1, "b": "hello"}, {"a": 2, "b": "world"}]"#,
     FieldType::List(FieldType::Class("Foo".to_string()).into()),
     [{"a": 1, "b": "hello"}, {"a": 2, "b": "world"}]
diff --git a/engine/baml-lib/jsonish/src/tests/test_maps.rs b/engine/baml-lib/jsonish/src/tests/test_maps.rs
new file mode 100644
index 000000000..ba734ec23
--- /dev/null
+++ b/engine/baml-lib/jsonish/src/tests/test_maps.rs
@@ -0,0 +1,45 @@
+use super::*;
+
+test_deserializer!(
+    test_map,
+    "",
+    r#"{"a": "b"}"#,
+    FieldType::map(FieldType::string(), FieldType::string()).into(),
+    {"a": "b"}
+);
+
+test_deserializer!(
+    test_map_with_quotes,
+    "",
+    r#"{"\"a\"": "\"b\""}"#,
+    FieldType::map(FieldType::string(), FieldType::string()).into(),
+    {"\"a\"": "\"b\""}
+);
+
+test_deserializer!(
+    test_map_with_extra_text,
+    "",
+    r#"{"a": "b"} is the output."#,
+    FieldType::map(FieldType::string(), FieldType::string()).into(),
+    {"a": "b"}
+);
+
+test_deserializer!(
+    test_map_with_invalid_extra_text,
+    "",
+    r#"{a: b} is the output."#,
+    FieldType::map(FieldType::string(), FieldType::string()).into(),
+    {"a": "b"}
+);
+
+test_deserializer!(
+    test_map_with_object_values,
+    r#"
+    class Foo {
+        a int
+        b string
+    }"#,
+    r#"{first: {"a": 1, "b": "hello"}, 'second': {"a": 2, "b": "world"}}"#,
+    FieldType::map(FieldType::string(), FieldType::class("Foo")).into(),
+    {"first":{"a": 1, "b": "hello"}, "second":{"a": 2, "b": "world"}}
+);