diff --git a/policy/v1beta1/cfg.pb.go b/policy/v1beta1/cfg.pb.go
index 3fb12fb531..dd72e0615c 100644
--- a/policy/v1beta1/cfg.pb.go
+++ b/policy/v1beta1/cfg.pb.go
@@ -65,9 +65,12 @@ const _ = proto.GoGoProtoPackageIsVersion2 // please upgrade the proto package
 type Rule_HeaderOperationTemplate_Operation int32
 
 const (
+	// Replace a header by name.
 	REPLACE Rule_HeaderOperationTemplate_Operation = 0
-	REMOVE  Rule_HeaderOperationTemplate_Operation = 1
-	APPEND  Rule_HeaderOperationTemplate_Operation = 2
+	// Remove a header by name. Values are ignored.
+	REMOVE Rule_HeaderOperationTemplate_Operation = 1
+	// Append values to the existing header values.
+	APPEND Rule_HeaderOperationTemplate_Operation = 2
 )
 
 var Rule_HeaderOperationTemplate_Operation_name = map[int32]string{
@@ -258,10 +261,10 @@ type Rule struct {
 	Match string `protobuf:"bytes,1,opt,name=match,proto3" json:"match,omitempty"`
 	// Optional. The actions that will be executed when match evaluates to `true`.
 	Actions []*Action `protobuf:"bytes,2,rep,name=actions" json:"actions,omitempty"`
-	// Optional. Templatized operations on the request headers using attributes produced by the
+	// Optional. Templatized operations on the request headers using values produced by the
 	// rule actions.
 	RequestHeaderOperations []*Rule_HeaderOperationTemplate `protobuf:"bytes,3,rep,name=request_header_operations,json=requestHeaderOperations" json:"request_header_operations,omitempty"`
-	// Optional. Templatized operations on the response headers using attributes produced by the
+	// Optional. Templatized operations on the response headers using values produced by the
 	// rule actions.
 	ResponseHeaderOperations []*Rule_HeaderOperationTemplate `protobuf:"bytes,4,rep,name=response_header_operations,json=responseHeaderOperations" json:"response_header_operations,omitempty"`
 	// $hide_from_docs
@@ -312,11 +315,20 @@ func (m *Rule) GetSampling() *Sampling {
 	return nil
 }
 
-// A template for an HTTP header manipulation.
+// A template for an HTTP header manipulation. Values in the template are expressions
+// that may reference action outputs by name. For example, if an action `x` produces an output
+// with a field `f`, then the header value expressions may use attribute `x.output.f` to reference
+// the field value:
+// ```yaml
+// request_header_operations:
+// - name: x-istio-header
+//   values:
+//   - x.output.f
+// ```
 type Rule_HeaderOperationTemplate struct {
-	// Required. Header name.
+	// Required. Header name literal value.
 	Name string `protobuf:"bytes,1,opt,name=name,proto3" json:"name,omitempty"`
-	// Optional. Header values to replace or append.
+	// Optional. Header value expressions.
 	Values []string `protobuf:"bytes,2,rep,name=values" json:"values,omitempty"`
 	// Optional. Header operation type. Default operation is to replace the value of the header by name.
 	Operation Rule_HeaderOperationTemplate_Operation `protobuf:"varint,3,opt,name=operation,proto3,enum=istio.policy.v1beta1.Rule_HeaderOperationTemplate_Operation" json:"operation,omitempty"`
diff --git a/policy/v1beta1/cfg.proto b/policy/v1beta1/cfg.proto
index 08491be43d..786df844d2 100644
--- a/policy/v1beta1/cfg.proto
+++ b/policy/v1beta1/cfg.proto
@@ -127,31 +127,45 @@ message Rule {
   // Optional. The actions that will be executed when match evaluates to `true`.
   repeated Action actions = 2;
 
-  // A template for an HTTP header manipulation.
+  // A template for an HTTP header manipulation. Values in the template are expressions
+  // that may reference action outputs by name. For example, if an action `x` produces an output
+  // with a field `f`, then the header value expressions may use attribute `x.output.f` to reference
+  // the field value:
+  // ```yaml
+  // request_header_operations:
+  // - name: x-istio-header
+  //   values:
+  //   - x.output.f
+  // ```
   message HeaderOperationTemplate {
 
-    // Required. Header name.
+    // Required. Header name literal value.
     string name = 1;
 
-    // Optional. Header values to replace or append.
+    // Optional. Header value expressions.
     repeated string values = 2;
 
     // Header operation type.
     enum Operation {
-      REPLACE = 0;  // replaces the header with the given name
-      REMOVE = 1;   // removes the header with the given name (the value is ignored)
-      APPEND = 2;   // appends the values to the existing values (preserving existing values)
+      // Replace a header by name.
+      REPLACE = 0;
+
+      // Remove a header by name. Values are ignored.
+      REMOVE = 1;
+
+      // Append values to the existing header values.
+      APPEND = 2;
     }
 
     // Optional. Header operation type. Default operation is to replace the value of the header by name.
     Operation operation = 3;
   }
 
-  // Optional. Templatized operations on the request headers using attributes produced by the
+  // Optional. Templatized operations on the request headers using values produced by the
   // rule actions.
   repeated HeaderOperationTemplate request_header_operations = 3;
 
-  // Optional. Templatized operations on the response headers using attributes produced by the
+  // Optional. Templatized operations on the response headers using values produced by the
   // rule actions.
   repeated HeaderOperationTemplate response_header_operations = 4;
 
diff --git a/policy/v1beta1/istio.policy.v1beta1.pb.html b/policy/v1beta1/istio.policy.v1beta1.pb.html
index fde19d018c..2cd47ce3ee 100644
--- a/policy/v1beta1/istio.policy.v1beta1.pb.html
+++ b/policy/v1beta1/istio.policy.v1beta1.pb.html
@@ -633,7 +633,7 @@ <h2 id="Rule">Rule</h2>
 <td><code>requestHeaderOperations</code></td>
 <td><code><a href="#Rule-HeaderOperationTemplate">Rule.HeaderOperationTemplate[]</a></code></td>
 <td>
-<p>Optional. Templatized operations on the request headers using attributes produced by the
+<p>Optional. Templatized operations on the request headers using values produced by the
 rule actions.</p>
 
 </td>
@@ -642,7 +642,7 @@ <h2 id="Rule">Rule</h2>
 <td><code>responseHeaderOperations</code></td>
 <td><code><a href="#Rule-HeaderOperationTemplate">Rule.HeaderOperationTemplate[]</a></code></td>
 <td>
-<p>Optional. Templatized operations on the response headers using attributes produced by the
+<p>Optional. Templatized operations on the response headers using values produced by the
 rule actions.</p>
 
 </td>
@@ -652,7 +652,16 @@ <h2 id="Rule">Rule</h2>
 </section>
 <h2 id="Rule-HeaderOperationTemplate">Rule.HeaderOperationTemplate</h2>
 <section>
-<p>A template for an HTTP header manipulation.</p>
+<p>A template for an HTTP header manipulation. Values in the template are expressions
+that may reference action outputs by name. For example, if an action <code>x</code> produces an output
+with a field <code>f</code>, then the header value expressions may use attribute <code>x.output.f</code> to reference
+the field value:</p>
+
+<pre><code class="language-yaml">request_header_operations:
+- name: x-istio-header
+  values:
+  - x.output.f
+</code></pre>
 
 <table class="message-fields">
 <thead>
@@ -667,7 +676,7 @@ <h2 id="Rule-HeaderOperationTemplate">Rule.HeaderOperationTemplate</h2>
 <td><code>name</code></td>
 <td><code>string</code></td>
 <td>
-<p>Required. Header name.</p>
+<p>Required. Header name literal value.</p>
 
 </td>
 </tr>
@@ -675,7 +684,7 @@ <h2 id="Rule-HeaderOperationTemplate">Rule.HeaderOperationTemplate</h2>
 <td><code>values</code></td>
 <td><code>string[]</code></td>
 <td>
-<p>Optional. Header values to replace or append.</p>
+<p>Optional. Header value expressions.</p>
 
 </td>
 </tr>
@@ -705,21 +714,21 @@ <h2 id="Rule-HeaderOperationTemplate-Operation">Rule.HeaderOperationTemplate.Ope
 <tr id="Rule-HeaderOperationTemplate-Operation-REPLACE">
 <td><code>REPLACE</code></td>
 <td>
-<p>replaces the header with the given name</p>
+<p>Replace a header by name.</p>
 
 </td>
 </tr>
 <tr id="Rule-HeaderOperationTemplate-Operation-REMOVE">
 <td><code>REMOVE</code></td>
 <td>
-<p>removes the header with the given name (the value is ignored)</p>
+<p>Remove a header by name. Values are ignored.</p>
 
 </td>
 </tr>
 <tr id="Rule-HeaderOperationTemplate-Operation-APPEND">
 <td><code>APPEND</code></td>
 <td>
-<p>appends the values to the existing values (preserving existing values)</p>
+<p>Append values to the existing header values.</p>
 
 </td>
 </tr>