diff --git a/anyuuid_test.go b/anyuuid_test.go
new file mode 100644
index 0000000..516fd51
--- /dev/null
+++ b/anyuuid_test.go
@@ -0,0 +1,70 @@
+package typeid_test
+
+import (
+	"encoding/json"
+	"fmt"
+
+	"github.com/go-chi/typeid"
+)
+
+type Mode string
+
+const (
+	ModeLive    Mode = "key"
+	ModeSandbox Mode = "key_sandbox"
+)
+
+type ApiKeyID struct {
+	typeid.AnyUUID
+}
+
+func NewApiKeyID(mode Mode) ApiKeyID {
+	u, err := typeid.NewAnyUUID(string(mode))
+	if err != nil {
+		panic(err) // can't happen unless crypto/rand is not available
+	}
+	return ApiKeyID{AnyUUID: u}
+}
+
+func (id *ApiKeyID) UnmarshalText(data []byte) error {
+	if err := id.AnyUUID.UnmarshalText(data); err != nil {
+		return err
+	}
+	switch id.AnyUUID.Prefix() {
+	case string(ModeLive), string(ModeSandbox):
+		return nil
+	default:
+		return fmt.Errorf("invalid api key prefix: %q", id.AnyUUID.Prefix())
+	}
+}
+
+type Request struct {
+	ID          ApiKeyID `json:"id"`
+	Description string   `json:"description"`
+}
+
+func ExampleAnyUUID_json() {
+	// Sandbox
+	data, _ := json.Marshal(Request{ID: NewApiKeyID(ModeSandbox), Description: "Sandbox API Key"})
+	var sandboxRequest Request
+	_ = json.Unmarshal(data, &sandboxRequest)
+
+	// Live
+	data, _ = json.Marshal(Request{ID: NewApiKeyID(ModeLive), Description: "Live API Key"})
+	var liveRequest Request
+	_ = json.Unmarshal(data, &liveRequest)
+
+	// Invalid prefix, expect error
+	data = []byte(`{"id":"key_invalid_prefix_01jcp1ss00edg828t5cy4tqkff", "description":"Invalid API Key"}`)
+	var unknownRequest Request
+	err := json.Unmarshal(data, &unknownRequest)
+
+	fmt.Println(sandboxRequest.ID.Prefix())
+	fmt.Println(liveRequest.ID.Prefix())
+	fmt.Println(unknownRequest.ID.Prefix(), err)
+
+	// Output:
+	// key_sandbox
+	// key
+	// key_invalid_prefix invalid api key prefix: "key_invalid_prefix"
+}