diff --git a/README.md b/README.md
index 7660d90..868b1d4 100644
--- a/README.md
+++ b/README.md
@@ -145,7 +145,7 @@ metadata:
   name: basic
 spec:
   params:
-     custom_key: custom_value
+    custom_key: custom_value
   source: oci://ghcr.io/kcl-lang/crossplane-xnetwork-kcl-function
 ```
 
@@ -331,7 +331,7 @@ metadata:
 spec:
   source: |
     import base64
-    
+
     # Omit other logic
     ocds = option("params").ocds
     details = {
@@ -363,6 +363,83 @@ spec:
     }
 ```
 
+### Extra resources
+By defining one or more special `ExtraResources`, you can ask Crossplane to retrieve additional resources from the local cluster and make them available to your templates. See the [docs](https://github.com/crossplane/crossplane/blob/main/design/design-doc-composition-functions-extra-resources.md) for more information.
+
+```yaml
+apiVersion: krm.kcl.dev/v1alpha1
+kind: KCLInput
+metadata:
+  name: basic
+spec:
+  source: |
+    # Omit other logic
+    details = {
+        apiVersion: "meta.krm.kcl.dev/v1alpha1"
+        kind: "ExtraResources"
+        requirements = {
+            foo = {
+                apiVersion: "example.com/v1beta1",
+                kind: "Foo",
+                matchLabels: {
+                    "foo": "bar"
+                }
+            },
+            bar = {
+                apiVersion: "example.com/v1beta1",
+                kind: "Bar",
+                matchName: "my-bar"
+            }
+        }
+    }
+
+    # Omit other composite logics.
+    items = [
+        details
+        # Omit other return resources.
+    ]
+```
+You can retrieve the extra resources either via labels with `matchLabels` or via name with `matchName: somename`.
+
+This will result in Crossplane receiving the requested resources and make them available with the following format.
+```yaml
+foo:
+- Resource:
+    apiVersion: example.com/v1beta1
+    kind: Foo
+    metadata:
+      labels:
+        foo: bar
+    # Omitted for brevity
+- Resource:
+    apiVersion: example.com/v1beta1
+    kind: Foo
+    metadata:
+      labels:
+        foo: bar
+    # Omit for brevity
+bar:
+- Resource:
+    apiVersion: example.com/v1beta1
+    kind: Bar
+    metadata:
+      name: my-bar
+    # Omitted for brevity
+```
+You can access the retrieved resources in your code like this:
+```yaml
+apiVersion: krm.kcl.dev/v1alpha1
+kind: KCLInput
+metadata:
+  name: basic
+spec:
+  source: |
+    er = option("params")?.extraResources
+    
+    name = er?.bar[0]?.Resource?.metadata?.name or ""
+    # Omit other logic
+```
+
 ### Patching the XR status field
 
 You can read the XR, patch it with the status field and return the new patched XR in the `item` result like this
diff --git a/examples/default/extra_resources/Makefile b/examples/default/extra_resources/Makefile
new file mode 100644
index 0000000..f17dba7
--- /dev/null
+++ b/examples/default/extra_resources/Makefile
@@ -0,0 +1,2 @@
+run:
+	crossplane render --verbose xr.yaml composition.yaml functions.yaml -r --extra-resources extra_resources.yaml
diff --git a/examples/default/extra_resources/README.md b/examples/default/extra_resources/README.md
new file mode 100644
index 0000000..380cf1d
--- /dev/null
+++ b/examples/default/extra_resources/README.md
@@ -0,0 +1,62 @@
+# Example Manifests
+
+You can run your function locally and test it using `crossplane render`
+with these example manifests.
+
+```shell
+# Run the function locally
+$ go run . --insecure --debug
+```
+
+```shell
+# Then, in another terminal, call it with these example manifests
+$ crossplane render --verbose xr.yaml composition.yaml functions.yaml -r --extra-resources extra_resources.yaml
+---
+---
+apiVersion: example.crossplane.io/v1beta1
+kind: XR
+metadata:
+  name: example
+status:
+  conditions:
+  - lastTransitionTime: "2024-01-01T00:00:00Z"
+    message: 'Unready resources: another-awesome-dev-bucket, my-awesome-dev-bucket'
+    reason: Creating
+    status: "False"
+    type: Ready
+---
+apiVersion: example/v1alpha1
+kind: Foo
+metadata:
+  annotations:
+    crossplane.io/composition-resource-name: another-awesome-dev-bucket
+  generateName: example-
+  labels:
+    crossplane.io/composite: example
+  name: another-awesome-dev-bucket
+  ownerReferences:
+  - apiVersion: example.crossplane.io/v1beta1
+    blockOwnerDeletion: true
+    controller: true
+    kind: XR
+    name: example
+    uid: ""
+---
+apiVersion: example/v1alpha1
+kind: Foo
+metadata:
+  annotations:
+    crossplane.io/composition-resource-name: my-awesome-dev-bucket
+  generateName: example-
+  labels:
+    crossplane.io/composite: example
+  name: my-awesome-dev-bucket
+  ownerReferences:
+  - apiVersion: example.crossplane.io/v1beta1
+    blockOwnerDeletion: true
+    controller: true
+    kind: XR
+    name: example
+    uid: ""
+
+```
diff --git a/examples/default/extra_resources/composition.yaml b/examples/default/extra_resources/composition.yaml
new file mode 100644
index 0000000..44a88e2
--- /dev/null
+++ b/examples/default/extra_resources/composition.yaml
@@ -0,0 +1,54 @@
+apiVersion: apiextensions.crossplane.io/v1
+kind: Composition
+metadata:
+  name: function-template-go
+spec:
+  compositeTypeRef:
+    apiVersion: example.crossplane.io/v1beta1
+    kind: XR
+  mode: Pipeline
+  pipeline:
+  - step: normal
+    functionRef:
+      name: kcl-function
+    input:
+      apiVersion: krm.kcl.dev/v1alpha1
+      kind: KCLInput
+      metadata:
+        annotations:
+          "krm.kcl.dev/default_ready": "True"
+        name: basic
+      spec:
+        source: |
+          oxr = option("params").oxr
+          er = option("params")?.extraResources
+        
+          foo = [{
+            apiVersion: "example/v1alpha1"
+            kind: "Foo"
+            metadata = {
+              name: k.Resource.metadata.name
+            }
+          } for k in er?.bucket] if er?.bucket else []
+          
+          dxr = {
+              **oxr
+          }
+          
+          details = {
+              apiVersion: "meta.krm.kcl.dev/v1alpha1"
+              kind: "ExtraResources"
+              requirements = {
+                  bucket = {
+                      apiVersion: "s3.aws.upbound.io/v1beta1",
+                      kind: "Bucket",
+                      matchLabels: {
+                          "foo": "bar"
+                      }
+                  }
+              }
+          }
+          items = [
+              details
+              dxr 
+          ] + foo
diff --git a/examples/default/extra_resources/extra_resources.yaml b/examples/default/extra_resources/extra_resources.yaml
new file mode 100644
index 0000000..8d5a780
--- /dev/null
+++ b/examples/default/extra_resources/extra_resources.yaml
@@ -0,0 +1,29 @@
+apiVersion: s3.aws.upbound.io/v1beta1
+kind: Bucket
+metadata:
+  annotations:
+    crossplane.io/external-name: my-awesome-dev-bucket
+  labels:
+    foo: bar
+  name: my-awesome-dev-bucket
+spec:
+  forProvider:
+    region: us-west-1
+status:
+  atProvider:
+    id: random-bucket-id
+---
+apiVersion: s3.aws.upbound.io/v1beta1
+kind: Bucket
+metadata:
+  annotations:
+    crossplane.io/external-name: my-awesome-dev-bucket
+  labels:
+    foo: bar
+  name: another-awesome-dev-bucket
+spec:
+  forProvider:
+    region: us-west-1
+status:
+  atProvider:
+    id: random-bucket-id
diff --git a/examples/default/extra_resources/functions.yaml b/examples/default/extra_resources/functions.yaml
new file mode 100644
index 0000000..d5679cb
--- /dev/null
+++ b/examples/default/extra_resources/functions.yaml
@@ -0,0 +1,9 @@
+apiVersion: pkg.crossplane.io/v1beta1
+kind: Function
+metadata:
+  name: kcl-function
+  annotations:
+    # This tells crossplane render to connect to the function locally.
+    render.crossplane.io/runtime: Development
+spec:
+  package: xpkg.upbound.io/crossplane-contrib/function-kcl:latest
diff --git a/examples/default/extra_resources/xr.yaml b/examples/default/extra_resources/xr.yaml
new file mode 100644
index 0000000..67aa59f
--- /dev/null
+++ b/examples/default/extra_resources/xr.yaml
@@ -0,0 +1,6 @@
+apiVersion: example.crossplane.io/v1beta1
+kind: XR
+metadata:
+  name: example
+spec:
+  count: 1