diff --git a/src/main/java/com/github/sttk/cliargs/Cmd.java b/src/main/java/com/github/sttk/cliargs/Cmd.java
index 2301145..cdf5bbf 100644
--- a/src/main/java/com/github/sttk/cliargs/Cmd.java
+++ b/src/main/java/com/github/sttk/cliargs/Cmd.java
@@ -12,6 +12,7 @@
 import static java.util.Collections.emptyMap;
 import java.util.List;
 import java.util.Map;
+import java.util.StringJoiner;
 
 /**
  * Is the class which contains a command name, command arguments, and option
@@ -24,6 +25,20 @@ public class Cmd {
   private final List<String> args;
   private final Map<String, List<?>> opts;
 
+  /**
+   * Outputs a string of the content of this object.
+   *
+   * @return  A content string of this object.
+   */
+  @Override
+  public String toString() {
+    return new StringJoiner(", ", "Cmd{", "}")
+      .add("name=" + this.name)
+      .add("args=" + this.args)
+      .add("opts=" + this.opts)
+      .toString();
+  }
+
   /**
    * Is the constructor which takes the fields of this class.
    *
diff --git a/src/main/java/com/github/sttk/cliargs/OptCfg.java b/src/main/java/com/github/sttk/cliargs/OptCfg.java
index 14a947f..fbea2cf 100644
--- a/src/main/java/com/github/sttk/cliargs/OptCfg.java
+++ b/src/main/java/com/github/sttk/cliargs/OptCfg.java
@@ -23,6 +23,7 @@
 import java.math.BigInteger;
 import java.util.List;
 import java.util.ArrayList;
+import java.util.StringJoiner;
 import com.github.sttk.exception.ReasonedException;
 
 /**
@@ -101,6 +102,27 @@ public class OptCfg {
    */
   public final Postparser<?> postparser;
 
+  /**
+   * Outputs a string of the content of this object.
+   *
+   * @return  A content string of this object.
+   */
+  @Override
+  public String toString() {
+    return new StringJoiner(", ", "OptCfg{", "}")
+      .add("storeKey=" + this.storeKey)
+      .add("names=" + this.names)
+      .add("hasArg=" + this.hasArg)
+      .add("isArray=" + this.isArray)
+      .add("type=" + this.type)
+      .add("defaults=" + this.defaults)
+      .add("desc=" + this.desc)
+      .add("argInHelp=" + this.argInHelp)
+      .add("converter=" + this.converter)
+      .add("postparser=" + this.postparser)
+      .toString();
+  }
+
   /**
    * Is the constructor that takes the all field values as parameters.
    * <p>
diff --git a/src/test/java/com/github/sttk/cliargs/CmdTest.java b/src/test/java/com/github/sttk/cliargs/CmdTest.java
index abd1dfd..6da6e39 100644
--- a/src/test/java/com/github/sttk/cliargs/CmdTest.java
+++ b/src/test/java/com/github/sttk/cliargs/CmdTest.java
@@ -111,4 +111,19 @@ void testGetArgs_returnedListIsUnmodifiable() {
       fail();
     } catch (UnsupportedOperationException e) {}
   }
+
+  @Test
+  void testToString() {
+    var args = new ArrayList<>(List.of("a0", "a1", "a2"));
+
+    var opts = new HashMap<String, List<?>>();
+    opts.put("o0", new ArrayList<Integer>(List.of(123, 456)));
+    opts.put("o1", new ArrayList<String>());
+
+    var cmd = new Cmd("foo", args, opts);
+
+    assertThat(cmd.toString()).isEqualTo(
+      "Cmd{name=foo, args=[a0, a1, a2], opts={o0=[123, 456], o1=[]}}"
+    );
+  }
 }
diff --git a/src/test/java/com/github/sttk/cliargs/OptCfgTest.java b/src/test/java/com/github/sttk/cliargs/OptCfgTest.java
index 2db16e5..d87de7b 100644
--- a/src/test/java/com/github/sttk/cliargs/OptCfgTest.java
+++ b/src/test/java/com/github/sttk/cliargs/OptCfgTest.java
@@ -664,4 +664,39 @@ void testConstructor_withNamedParam_full() {
     assertThat(optCfg.converter).isEqualTo(c);
     assertThat(optCfg.postparser).isEqualTo(p);
   }
+
+  @Test
+  void testToString() {
+    var c = new IntConverter();
+    Postparser<Integer> p = i -> {};
+
+    @SuppressWarnings("unchecked")
+    var optCfg = new OptCfg(
+      desc("The option description"),
+      isArray(true),
+      names("foo-bar", "f"),
+      storeKey("FooBar"),
+      converter(c),
+      postparser(p),
+      hasArg(true),
+      argInHelp("<num>"),
+      type(int.class),
+      defaults(123, 45)
+    );
+
+    assertThat(optCfg.toString()).matches(
+      "OptCfg\\{" +
+      "storeKey=FooBar, " +
+      "names=\\[foo-bar, f\\], " +
+      "hasArg=true, " +
+      "isArray=true, " +
+      "type=int, " +
+      "defaults=\\[123, 45\\], " +
+      "desc=The option description, " +
+      "argInHelp=\\<num\\>, " +
+      "converter=[^,]*, " +
+      "postparser=[^,]*" +
+      "}"
+    );
+  }
 }