diff --git a/crates/goose/src/agents/extension.rs b/crates/goose/src/agents/extension.rs
index 9f1daa6cd279..de63751c1e56 100644
--- a/crates/goose/src/agents/extension.rs
+++ b/crates/goose/src/agents/extension.rs
@@ -11,6 +11,7 @@ use once_cell::sync::Lazy;
 use rmcp::model::Tool;
 use rmcp::service::ClientInitializeError;
 use rmcp::ServiceError as ClientError;
+use serde::Deserializer;
 use serde::{Deserialize, Serialize};
 use thiserror::Error;
 use tracing::warn;
@@ -216,6 +217,7 @@ pub enum ExtensionConfig {
         /// The name used to identify this extension
         name: String,
         #[serde(default)]
+        #[serde(deserialize_with = "deserialize_null_with_default")]
         #[schema(required)]
         description: String,
         uri: String,
@@ -237,6 +239,7 @@ pub enum ExtensionConfig {
         /// The name used to identify this extension
         name: String,
         #[serde(default)]
+        #[serde(deserialize_with = "deserialize_null_with_default")]
         #[schema(required)]
         description: String,
         cmd: String,
@@ -257,6 +260,7 @@ pub enum ExtensionConfig {
         /// The name used to identify this extension
         name: String,
         #[serde(default)]
+        #[serde(deserialize_with = "deserialize_null_with_default")]
         #[schema(required)]
         description: String,
         display_name: Option<String>, // needed for the UI
@@ -271,7 +275,7 @@ pub enum ExtensionConfig {
     Platform {
         /// The name used to identify this extension
         name: String,
-        #[serde(default)]
+        #[serde(deserialize_with = "deserialize_null_with_default")]
         #[schema(required)]
         description: String,
         #[serde(default)]
@@ -284,7 +288,7 @@ pub enum ExtensionConfig {
     StreamableHttp {
         /// The name used to identify this extension
         name: String,
-        #[serde(default)]
+        #[serde(deserialize_with = "deserialize_null_with_default")]
         #[schema(required)]
         description: String,
         uri: String,
@@ -307,7 +311,7 @@ pub enum ExtensionConfig {
     Frontend {
         /// The name used to identify this extension
         name: String,
-        #[serde(default)]
+        #[serde(deserialize_with = "deserialize_null_with_default")]
         #[schema(required)]
         description: String,
         /// The tools provided by the frontend
@@ -324,7 +328,7 @@ pub enum ExtensionConfig {
     InlinePython {
         /// The name used to identify this extension
         name: String,
-        #[serde(default)]
+        #[serde(deserialize_with = "deserialize_null_with_default")]
         #[schema(required)]
         description: String,
         /// The Python code to execute
@@ -544,6 +548,15 @@ impl ExtensionInfo {
     }
 }
 
+fn deserialize_null_with_default<'de, D, T>(deserializer: D) -> Result<T, D::Error>
+where
+    T: Default + Deserialize<'de>,
+    D: Deserializer<'de>,
+{
+    let opt = Option::deserialize(deserializer)?;
+    Ok(opt.unwrap_or_default())
+}
+
 /// Information about the tool used for building prompts
 #[derive(Clone, Debug, Serialize, ToSchema)]
 pub struct ToolInfo {
@@ -568,3 +581,69 @@ impl ToolInfo {
         }
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use crate::agents::*;
+
+    #[test]
+    fn test_deserialize_missing_description() {
+        let config: ExtensionConfig = serde_yaml::from_str(
+            "enabled: true
+type: builtin
+name: developer
+display_name: Developer
+timeout: 300
+bundled: true
+available_tools: []",
+        )
+        .unwrap();
+        if let ExtensionConfig::Builtin { description, .. } = config {
+            assert_eq!(description, "")
+        } else {
+            panic!("unexpected result of deserialization: {}", config)
+        }
+    }
+
+    #[test]
+    fn test_deserialize_null_description() {
+        let config: ExtensionConfig = serde_yaml::from_str(
+            "enabled: true
+type: builtin
+name: developer
+display_name: Developer
+description: null
+timeout: 300
+bundled: true
+available_tools: []
+",
+        )
+        .unwrap();
+        if let ExtensionConfig::Builtin { description, .. } = config {
+            assert_eq!(description, "")
+        } else {
+            panic!("unexpected result of deserialization: {}", config)
+        }
+    }
+
+    #[test]
+    fn test_deserialize_normal_description() {
+        let config: ExtensionConfig = serde_yaml::from_str(
+            "enabled: true
+type: builtin
+name: developer
+display_name: Developer
+description: description goes here
+timeout: 300
+bundled: true
+available_tools: []
+    ",
+        )
+        .unwrap();
+        if let ExtensionConfig::Builtin { description, .. } = config {
+            assert_eq!(description, "description goes here")
+        } else {
+            panic!("unexpected result of deserialization: {}", config)
+        }
+    }
+}