diff --git a/docs/usage/check_comment.md b/docs/usage/check_comment.md
index eb0b21c5..1407d5bb 100644
--- a/docs/usage/check_comment.md
+++ b/docs/usage/check_comment.md
@@ -63,7 +63,8 @@ try {
   console.log(result == CheckResult.ham ? "The comment is ham." : "The comment is spam.");
 }
 catch (error) {
-  console.log(`An error occurred: ${error}`);
+	const message = error instanceof Error ? error.message : String(error);
+	console.log(`An error occurred: ${message}`);
 }
 ```
 
diff --git a/docs/usage/submit_ham.md b/docs/usage/submit_ham.md
index c31f354e..75139bbe 100644
--- a/docs/usage/submit_ham.md
+++ b/docs/usage/submit_ham.md
@@ -50,6 +50,7 @@ try {
   console.log("The comment was successfully submitted as ham.");
 }
 catch (error) {
-  console.log(`An error occurred: ${error}`);
+	const message = error instanceof Error ? error.message : String(error);
+	console.log(`An error occurred: ${message}`);
 }
 ```
diff --git a/docs/usage/submit_spam.md b/docs/usage/submit_spam.md
index bc22296a..ff14a51d 100644
--- a/docs/usage/submit_spam.md
+++ b/docs/usage/submit_spam.md
@@ -52,6 +52,7 @@ try {
   console.log("The comment was successfully submitted as spam.");
 }
 catch (error) {
-  console.log(`An error occurred: ${error}`);
+	const message = error instanceof Error ? error.message : String(error);
+	console.log(`An error occurred: ${message}`);
 }
 ```
diff --git a/docs/usage/verify_key.md b/docs/usage/verify_key.md
index dfd077ff..85588479 100644
--- a/docs/usage/verify_key.md
+++ b/docs/usage/verify_key.md
@@ -38,7 +38,8 @@ try {
   console.log(isValid ? "The API key is valid." : "The API key is invalid.");
 }
 catch (error) {
-  console.log(`An error occurred: ${error}`);
+	const message = error instanceof Error ? error.message : String(error);
+	console.log(`An error occurred: ${message}`);
 }
 ```