diff --git a/tools/spectral/.spectral.yaml b/tools/spectral/.spectral.yaml
index eb4614f05..78017c105 100644
--- a/tools/spectral/.spectral.yaml
+++ b/tools/spectral/.spectral.yaml
@@ -184,6 +184,17 @@ rules:
           field: allow_diff
           pattern: "^true$"
 
+   no-slash-before-custom-method:
+    description: "Custom methods (e.g., ':applyItem') should not be preceded by a '/'."
+    message: "The path '{{path}}' contains a '/' before a custom method. Custom methods should not start with a '/'."
+    severity: error
+    given: "$.paths"
+    then:
+      field: "@key"
+      function: pattern
+      functionOptions:
+        notMatch: "/[^/]+/:[a-zA-Z]+$"
+
 overrides:
   - files: # load sample data has an issue with different path param names for different VERBS
       - "*.yaml#/paths/~1api~1atlas~1v1.0~1groups~1%7BgroupId%7D~1sampleDatasetLoad~1%7BsampleDatasetId%7D"