diff --git a/core/src/schema/idl/grammar.rs b/core/src/schema/idl/grammar.rs
index aa753f2..a1259c1 100644
--- a/core/src/schema/idl/grammar.rs
+++ b/core/src/schema/idl/grammar.rs
@@ -735,10 +735,19 @@ pub mod grammar {
         _close: (),
     }
 
-    /// `Name(key = value, key = value)` - a named call with keyword arguments.
+    /// `Name(key = value, key = value)` - a named call with keyword
+    /// arguments - or a bare `Name`, the same as `Name()`.
     #[derive(Debug, Clone)]
     pub struct AnnotationCall {
         pub name: Identifier,
+        #[rust_sitter::repeat(non_empty = false)]
+        pub call: Option<AnnotationCallArgs>,
+    }
+
+    /// The `(key = value, ...)` half of an [`AnnotationCall`], factored out
+    /// so the call can leave it off (same shape as `AnnotationAssignment`).
+    #[derive(Debug, Clone)]
+    pub struct AnnotationCallArgs {
         #[rust_sitter::leaf(text = "(")]
         _open: (),
         #[rust_sitter::delimited(
@@ -1592,6 +1601,13 @@ pub mod grammar {
         }
     }
 
+    impl AnnotationCall {
+        /// The call's arguments - none for a bare `Name`.
+        pub fn args(&self) -> &[AnnotationArg] {
+            self.call.as_ref().map(|c| c.args.as_slice()).unwrap_or_default()
+        }
+    }
+
     impl AnnotationValue {
         /// Render back to canonical text. Scalars round-trip as written; a
         /// list normalises to `[Name(a = 1, b = 2), ...]`.
@@ -1611,7 +1627,7 @@ pub mod grammar {
                         .iter()
                         .map(|call| {
                             let args: Vec<String> = call
-                                .args
+                                .args()
                                 .iter()
                                 .map(|a| {
                                     format!("{} = {}", a.name.text, a.value.as_text())
diff --git a/core/src/schema/ir/compiler/interpreter/incremental.rs b/core/src/schema/ir/compiler/interpreter/incremental.rs
index 58b7936..ddeebf1 100644
--- a/core/src/schema/ir/compiler/interpreter/incremental.rs
+++ b/core/src/schema/ir/compiler/interpreter/incremental.rs
@@ -544,7 +544,7 @@ fn annotation_units(annotations: &[&Annotation]) -> Vec<FrozenUnit> {
                     units.push(FrozenUnit::ValidatorRef {
                         name: call.name.text.clone(),
                         args: call
-                            .args
+                            .args()
                             .iter()
                             .map(|arg| FrozenUnit::Property {
                                 name: arg.name.text.clone(),
diff --git a/core/src/schema/ir/validation/validator.rs b/core/src/schema/ir/validation/validator.rs
index fba6ea7..9a0a46b 100644
--- a/core/src/schema/ir/validation/validator.rs
+++ b/core/src/schema/ir/validation/validator.rs
@@ -25,6 +25,8 @@ const DUPLICATE_VALIDATOR_ARGUMENT: DiagnosticCode =
     DiagnosticCode::error("validation::duplicate-validator-argument");
 const UNKNOWN_VALIDATOR_ARGUMENT: DiagnosticCode =
     DiagnosticCode::error("validation::unknown-validator-argument");
+const MISSING_VALIDATOR_ARGUMENT: DiagnosticCode =
+    DiagnosticCode::error("validation::missing-validator-argument");
 const VALIDATOR_ARGUMENT_TYPE_MISMATCH: DiagnosticCode =
     DiagnosticCode::error("validation::validator-argument-type-mismatch");
 const NOT_A_VALIDATOR: DiagnosticCode = DiagnosticCode::error("validation::not-a-validator");
@@ -436,6 +438,21 @@ pub fn validate_with(
                                 }
                             }
                         }
+
+                        // Every property without a default has to be given
+                        // - a bare `Name` gives none.
+                        let fields = validator_fields.get(vname.as_str()).copied().unwrap_or_default();
+                        for field in fields {
+                            if let FrozenUnit::Field { name: prop, default: None, .. } = field {
+                                if !seen.contains(&prop.as_str()) {
+                                    errors.push(Diagnostic { code: MISSING_VALIDATOR_ARGUMENT, help: None, secondary: None, severity_override: None,
+                                        message: format!("validator '{}' is missing argument '{}'", vname, prop),
+                                        context: field_ctx.clone(),
+                                        span: Some(*span),
+                                    });
+                                }
+                            }
+                        }
                     }
                 }
                 Some(other) if other != SymbolType::Import => {
diff --git a/core/tests/schema/ir/alias_validators.rs b/core/tests/schema/ir/alias_validators.rs
index f3e97cc..cb89617 100644
--- a/core/tests/schema/ir/alias_validators.rs
+++ b/core/tests/schema/ir/alias_validators.rs
@@ -163,3 +163,38 @@ fn a_stand_in_import_is_not_judged_against_a_validator() {
         ["validator 'Positive' applies to `u32`, not `Name`"]
     );
 }
+
+#[test]
+fn a_bare_validator_name_is_a_call_with_no_arguments() {
+    let units = IncrementalInterpreter::from_source(&format!(
+        "{BOUNDS}@validators = [Bounds, Bounds(max = 5)]\ntype AccountName = string\n"
+    ));
+    let parameters = units
+        .iter()
+        .find_map(|u| match u {
+            FrozenUnit::TypeAlias { name, parameters, .. } if name == "AccountName" => Some(parameters),
+            _ => None,
+        })
+        .expect("the alias");
+    assert_eq!(
+        *parameters,
+        [
+            FrozenUnit::ValidatorRef { name: "Bounds".to_string(), args: vec![] },
+            FrozenUnit::ValidatorRef {
+                name: "Bounds".to_string(),
+                args: vec![FrozenUnit::Property { name: "max".to_string(), value: ConfigValue::Integer(5) }],
+            },
+        ]
+    );
+    assert!(validate(&units).is_ok());
+}
+
+#[test]
+fn a_bare_validator_name_still_needs_its_required_arguments() {
+    let code = "validator Range for u32 {\n    min: u32\n    validate {\n        \
+                assert(value >= params.min, \"{value.name}\")\n    }\n}\n\
+                @validators = [Range]\ntype Count = u32\n";
+    assert_eq!(messages(code), ["validator 'Range' is missing argument 'min'"]);
+    // Written out, it's fine - and so is leaving out one with a default.
+    assert!(messages(&code.replace("[Range]", "[Range(min = 1)]")).is_empty());
+}