diff --git a/tests/functional/syntax/test_concat.py b/tests/functional/syntax/test_concat.py
index 612b45622a..3ddd31eb02 100644
--- a/tests/functional/syntax/test_concat.py
+++ b/tests/functional/syntax/test_concat.py
@@ -117,6 +117,20 @@ def test_block_fail(assert_compile_failed, get_contract, bad_code, exc):
     assert_compile_failed(lambda: get_contract(bad_code), exc)
 
 
+def test_concat_type_mismatch_message_uses_readable_type_names():
+    code = """
+@external
+def foo() -> Bytes[64]:
+    return concat(123, b"x")
+    """
+    with pytest.raises(TypeMismatch) as e:
+        compiler.compile_code(code)
+
+    assert e.value.message == (
+        "Expected one of Bytes, String, bytesM but literal can only be cast as int104 or uint96."
+    )
+
+
 valid_list = [
     """
 @external
diff --git a/tests/functional/syntax/test_len.py b/tests/functional/syntax/test_len.py
index b8cc61df1d..c2b8721576 100644
--- a/tests/functional/syntax/test_len.py
+++ b/tests/functional/syntax/test_len.py
@@ -53,3 +53,31 @@ def foo() -> uint256:
 @pytest.mark.parametrize("good_code", valid_list)
 def test_list_success(good_code):
     assert compile_code(good_code) is not None
+
+
+def test_len_type_mismatch_message_uses_readable_type_names():
+    code = """
+@external
+def foo(inp: int128) -> uint256:
+    return len(inp)
+    """
+    with pytest.raises(TypeMismatch) as e:
+        compile_code(code)
+
+    assert e.value.message == (
+        "Given reference has type int128, expected one of String, Bytes, DynArray"
+    )
+
+
+def test_index_type_mismatch_message_uses_readable_type_names():
+    # `IntegerT.any()` renders its class-level `_id` (`integer`), not the
+    # applied per-instance name (`uint256`)
+    code = """
+@external
+def foo(x: DynArray[uint256, 3]) -> uint256:
+    return x[b"ab"]
+    """
+    with pytest.raises(TypeMismatch) as e:
+        compile_code(code)
+
+    assert e.value.message == "Expected integer but literal can only be cast as Bytes[2]."
diff --git a/vyper/semantics/analysis/getters.py b/vyper/semantics/analysis/getters.py
index c5c9ed1c1e..df66f7ab72 100644
--- a/vyper/semantics/analysis/getters.py
+++ b/vyper/semantics/analysis/getters.py
@@ -46,12 +46,12 @@ def generate_public_variable_getters(vyper_module: vy_ast.Module) -> None:
                 # type as the next arg
                 arg, annotation = annotation.slice.elements  # type: ignore
             elif annotation.value.get("id") == "DynArray":
-                arg = vy_ast.Name(id=type_._id)
+                arg = vy_ast.Name(id=type_.serialization_name)
                 annotation = annotation.slice.elements[0]  # type: ignore
             else:
                 # for other types, build an input arg node from the expected
                 # type and remove the outer `Subscript` from the annotation
-                arg = vy_ast.Name(id=type_._id)
+                arg = vy_ast.Name(id=type_.serialization_name)
                 annotation = annotation.value
             input_nodes.append(vy_ast.arg(arg=f"arg{i}", annotation=arg))
 
diff --git a/vyper/semantics/types/__init__.py b/vyper/semantics/types/__init__.py
index 412534973b..6986f47294 100644
--- a/vyper/semantics/types/__init__.py
+++ b/vyper/semantics/types/__init__.py
@@ -23,7 +23,14 @@ def _get_primitive_types():
     # are in the namespace instead of concrete type objects.
     res.extend([BytesT, StringT])
 
-    ret = {t._id: t for t in res}
+    ret = {}
+    for t in res:
+        if isinstance(t, type):
+            # parametrizable bytestring *classes* (e.g. `Bytes` for `Bytes[5]`)
+            # are registered under their declared name.
+            ret[t._id] = t
+        else:
+            ret[t.serialization_name] = t
     ret.update(_get_sequence_types())
 
     return ret
diff --git a/vyper/semantics/types/base.py b/vyper/semantics/types/base.py
index 3ffe5233e6..30848dccb3 100644
--- a/vyper/semantics/types/base.py
+++ b/vyper/semantics/types/base.py
@@ -24,6 +24,12 @@ class _GenericTypeAcceptor:
     def __repr__(self):
         return f"GenericTypeAcceptor({self.type_})"
 
+    def __str__(self):
+        # `.any()` hands us the *class*, whose `_id` names the type family
+        # (e.g. `String`, `bytesM`, `integer`). `TYPE_T` has no `_id` but is
+        # never stringified: its call sites reject a non-type arg first.
+        return self.type_._id
+
     def __init__(self, type_):
         self.type_ = type_
 
@@ -82,7 +88,12 @@ class VyperType:
 
     typeclass: str = None  # type: ignore
 
-    _id: str  # rename to `_name`
+    # Name of the type family (e.g. `bool`, `String`, `DynArray`, `integer`,
+    # `bytesM`). Types whose applied parameters are fused into a single source
+    # token (`uint256`, `bytes4`) expose the applied name via
+    # `serialization_name`; parameterized containers (e.g. `String[5]`,
+    # `DynArray[uint256, 3]`) render the applied name in `__repr__`.
+    _id: str
     _type_members: Optional[Dict] = None
     _valid_literal: Tuple = ()
     _invalid_locations: Tuple = ()
@@ -135,11 +146,19 @@ def __lt__(self, other):
 
     def __repr__(self):
         # TODO: add `pretty()` to the VyperType API?
+        return self.serialization_name
+
+    # The name used to refer to this type as a single source token (AST
+    # `to_dict` "name", namespace key, synthesized getter annotations).
+    # Defaults to `_id`; parametric primitives that fuse the applied
+    # parameters into the name (`uint256`, `bytes4`) override it.
+    @property
+    def serialization_name(self):
         return self._id
 
     # return a dict suitable for serializing in the AST
     def to_dict(self):
-        ret = {"name": self._id}
+        ret = {"name": self.serialization_name}
         if self.decl_node is not None:
             ret["type_decl_node"] = self.decl_node.get_id_dict()
         if self.typeclass is not None:
diff --git a/vyper/semantics/types/primitives.py b/vyper/semantics/types/primitives.py
index 12ee47afaf..8176af905b 100644
--- a/vyper/semantics/types/primitives.py
+++ b/vyper/semantics/types/primitives.py
@@ -57,6 +57,7 @@ def validate_literal(self, node: vy_ast.Constant) -> None:
 # one-word bytesM with m possible bytes set, e.g. bytes1..bytes32
 class BytesM_T(_PrimT):
     typeclass = "bytes_m"
+    _id = "bytesM"
 
     _valid_literal = (vy_ast.Hex,)
 
@@ -67,7 +68,7 @@ def __init__(self, m):
         self.m: int = m
 
     @property
-    def _id(self):
+    def serialization_name(self):
         return f"bytes{self.m}"
 
     @property
@@ -266,6 +267,7 @@ class IntegerT(NumericT):
     """
 
     typeclass = "integer"
+    _id = "integer"
 
     _valid_literal = (vy_ast.Int,)
     _equality_attrs = ("is_signed", "bits")
@@ -277,8 +279,8 @@ def __init__(self, is_signed, bits):
         self._is_signed = is_signed
         self._bits = bits
 
-    @cached_property
-    def _id(self):
+    @property
+    def serialization_name(self):
         u = "u" if not self.is_signed else ""
         return f"{u}int{self.bits}"