diff --git a/src/data/cel.rs b/src/data/cel.rs
index 0f71ce1..83f8167 100644
--- a/src/data/cel.rs
+++ b/src/data/cel.rs
@@ -5,6 +5,7 @@ use cel_interpreter::objects::{Key, Map, ValueType};
 use cel_interpreter::{Context, ExecutionError, ResolveResult, Value};
 use cel_parser::{parse, Expression as CelExpression, Member, ParseError};
 use chrono::{DateTime, FixedOffset};
+use log::debug;
 use proxy_wasm::types::{Bytes, Status};
 use serde_json::Value as JsonValue;
 use std::collections::hash_map::Entry;
@@ -441,6 +442,22 @@ fn properties<'e>(exp: &'e CelExpression, all: &mut Vec<Vec<&'e str>>, path: &mu
     }
 }
 
+#[allow(dead_code)]
+pub fn debug_all_well_known_attributes() {
+    let attributes = new_well_known_attribute_map();
+    attributes.iter().for_each(|(key, value_type)| {
+        match proxy_wasm::hostcalls::get_property(key.tokens()) {
+            Ok(opt_bytes) => match opt_bytes {
+                None => debug!("{:#?}({}): None", key, value_type),
+                Some(bytes) => debug!("{:#?}({}): {:?}", key, value_type, bytes),
+            },
+            Err(err) => {
+                debug!("{:#?}({}): (err) {:?}", key, value_type, err)
+            }
+        }
+    })
+}
+
 pub mod data {
     use crate::data::cel::Attribute;
     use cel_interpreter::objects::{Key, Map};
diff --git a/src/data/mod.rs b/src/data/mod.rs
index 0e1cc10..004ece6 100644
--- a/src/data/mod.rs
+++ b/src/data/mod.rs
@@ -11,3 +11,5 @@ pub use cel::Predicate;
 
 pub use property::get_property;
 pub use property::Path as PropertyPath;
+
+// pub use cel::debug_all_well_known_attributes;
diff --git a/src/filter/http_context.rs b/src/filter/http_context.rs
index e365ccd..e7e407f 100644
--- a/src/filter/http_context.rs
+++ b/src/filter/http_context.rs
@@ -7,6 +7,7 @@ use proxy_wasm::traits::{Context, HttpContext};
 use proxy_wasm::types::Action;
 use std::cell::RefCell;
 use std::rc::Rc;
+// use crate::data;
 
 pub struct Filter {
     pub context_id: u32,
@@ -94,6 +95,9 @@ impl HttpContext for Filter {
     fn on_http_request_headers(&mut self, _: usize, _: bool) -> Action {
         debug!("#{} on_http_request_headers", self.context_id);
 
+        // uncomment to debug log all well known attributes
+        // data::debug_all_well_known_attributes();
+
         match self
             .config
             .index