diff --git a/src/main/java/eu/mulk/jgvariant/core/Decoder.java b/src/main/java/eu/mulk/jgvariant/core/Decoder.java
index d0c0323..d30366e 100644
--- a/src/main/java/eu/mulk/jgvariant/core/Decoder.java
+++ b/src/main/java/eu/mulk/jgvariant/core/Decoder.java
@@ -12,6 +12,8 @@
 import java.util.Arrays;
 import java.util.List;
 import java.util.Optional;
+import org.apiguardian.api.API;
+import org.apiguardian.api.API.Status;
 import org.jetbrains.annotations.Nullable;
 
 /**
@@ -42,6 +44,7 @@
  * @param <T> the type that the {@link Decoder} can decode.
  */
 @SuppressWarnings("java:S1610")
+@API(status = Status.EXPERIMENTAL)
 public abstract class Decoder<T> {
 
   private Decoder() {}
diff --git a/src/main/java/eu/mulk/jgvariant/core/Signature.java b/src/main/java/eu/mulk/jgvariant/core/Signature.java
index bb03b94..d9de5f1 100644
--- a/src/main/java/eu/mulk/jgvariant/core/Signature.java
+++ b/src/main/java/eu/mulk/jgvariant/core/Signature.java
@@ -6,6 +6,8 @@
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Objects;
+import org.apiguardian.api.API;
+import org.apiguardian.api.API.Status;
 
 /**
  * A GVariant signature string.
@@ -24,6 +26,7 @@
  *       an array of 32-bit integers
  * </dl>
  */
+@API(status = Status.STABLE)
 public final class Signature {
 
   private final String signatureString;
diff --git a/src/main/java/eu/mulk/jgvariant/core/Variant.java b/src/main/java/eu/mulk/jgvariant/core/Variant.java
index 134a5e8..1438d9d 100644
--- a/src/main/java/eu/mulk/jgvariant/core/Variant.java
+++ b/src/main/java/eu/mulk/jgvariant/core/Variant.java
@@ -1,5 +1,8 @@
 package eu.mulk.jgvariant.core;
 
+import org.apiguardian.api.API;
+import org.apiguardian.api.API.Status;
+
 /**
  * A dynamically typed GVariant value carrying a {@link Signature} describing its type.
  *
@@ -23,4 +26,5 @@
  *     Integer}, {@link Long}, {@link String}, {@link java.util.Optional}, {@link java.util.List},
  *     {@link Object[]}, {@link Variant}.
  */
+@API(status = Status.EXPERIMENTAL)
 public record Variant(Signature signature, Object value) {}
diff --git a/src/main/java/module-info.java b/src/main/java/module-info.java
index 39e91b8..c0debad 100644
--- a/src/main/java/module-info.java
+++ b/src/main/java/module-info.java
@@ -8,6 +8,7 @@
 module eu.mulk.jgvariant.core {
   requires com.google.errorprone.annotations;
   requires org.jetbrains.annotations;
+  requires org.apiguardian.api;
 
   exports eu.mulk.jgvariant.core;
 }