diff --git a/crates/goose/src/agents/agent.rs b/crates/goose/src/agents/agent.rs
index 1fb2165aca50..4cbc6d87dc4f 100644
--- a/crates/goose/src/agents/agent.rs
+++ b/crates/goose/src/agents/agent.rs
@@ -33,6 +33,7 @@ use crate::conversation::message::{
     ActionRequiredData, Message, MessageContent, ProviderMetadata, SystemNotificationType,
     ToolRequest,
 };
+use crate::conversation::tool_result_serde::call_tool_result;
 use crate::conversation::{debug_conversation_fix, fix_conversation, Conversation};
 use crate::mcp_utils::ToolResult;
 use crate::permission::permission_inspector::PermissionInspector;
@@ -1123,6 +1124,8 @@ impl Agent {
 
                                         match item {
                                             ToolStreamItem::Result(output) => {
+                                                let output = call_tool_result::validate(output);
+
                                                 if enable_extension_request_ids.contains(&request_id)
                                                     && output.is_err()
                                                 {
diff --git a/crates/goose/src/conversation/mod.rs b/crates/goose/src/conversation/mod.rs
index 5f86c660aede..14ec1ef7bcac 100644
--- a/crates/goose/src/conversation/mod.rs
+++ b/crates/goose/src/conversation/mod.rs
@@ -6,7 +6,7 @@ use thiserror::Error;
 use utoipa::ToSchema;
 
 pub mod message;
-mod tool_result_serde;
+pub mod tool_result_serde;
 
 #[derive(Debug, Clone, Serialize, Deserialize, ToSchema, PartialEq)]
 pub struct Conversation(Vec<Message>);
diff --git a/crates/goose/src/conversation/tool_result_serde.rs b/crates/goose/src/conversation/tool_result_serde.rs
index ef359e280127..1aea142929b5 100644
--- a/crates/goose/src/conversation/tool_result_serde.rs
+++ b/crates/goose/src/conversation/tool_result_serde.rs
@@ -102,7 +102,17 @@ pub mod call_tool_result {
             },
         }
 
-        let format = ResultFormat::deserialize(deserializer)?;
+        let original_value = serde_json::Value::deserialize(deserializer)?;
+
+        let format = ResultFormat::deserialize(&original_value).map_err(|e| {
+            tracing::debug!(
+                "Failed to deserialize call_tool_result: {}. Original data: {}",
+                e,
+                serde_json::to_string(&original_value)
+                    .unwrap_or_else(|_| "<invalid json>".to_string())
+            );
+            serde::de::Error::custom(e)
+        })?;
 
         match format {
             ResultFormat::NewSuccess { status, value } => {
@@ -141,4 +151,87 @@ pub mod call_tool_result {
             }
         }
     }
+
+    pub fn validate(result: ToolResult<CallToolResult>) -> ToolResult<CallToolResult> {
+        match &result {
+            Ok(call_tool_result) => match serde_json::to_string(call_tool_result) {
+                Ok(json_str) => match serde_json::from_str::<CallToolResult>(&json_str) {
+                    Ok(_) => result,
+                    Err(e) => {
+                        tracing::error!("CallToolResult failed validation by deserialization: {}. Original data: {}", e, json_str);
+                        Err(ErrorData {
+                            code: ErrorCode::INTERNAL_ERROR,
+                            message: Cow::from(format!("Tool result validation failed: {}", e)),
+                            data: None,
+                        })
+                    }
+                },
+                Err(e) => {
+                    tracing::error!("CallToolResult failed serialization: {}", e);
+                    Err(ErrorData {
+                        code: ErrorCode::INTERNAL_ERROR,
+                        message: Cow::from(format!("Tool result serialization failed: {}", e)),
+                        data: None,
+                    })
+                }
+            },
+            Err(_) => result,
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use rmcp::model::{CallToolResult, Content, ErrorCode, ErrorData};
+    use std::borrow::Cow;
+    #[test]
+    fn test_validate_accepts_valid_call_tool_result() {
+        let valid_result = CallToolResult {
+            content: vec![Content::text("test")],
+            is_error: Some(false),
+            structured_content: None,
+            meta: None,
+        };
+
+        let tool_result: ToolResult<CallToolResult> = Ok(valid_result);
+        let validated = call_tool_result::validate(tool_result);
+
+        assert!(
+            validated.is_ok(),
+            "Expected validation to pass for valid CallToolResult"
+        );
+    }
+    #[test]
+    fn test_validate_returns_error_for_invalid_calltoolresult() {
+        let valid_result = CallToolResult {
+            content: vec![],
+            is_error: Some(false),
+            structured_content: None,
+            meta: None,
+        };
+
+        let tool_result: ToolResult<CallToolResult> = Ok(valid_result);
+        let validated = call_tool_result::validate(tool_result);
+
+        assert!(validated.is_err());
+        assert!(validated
+            .unwrap_err()
+            .message
+            .contains("Tool result validation failed"))
+    }
+
+    #[test]
+    fn test_validate_passes_through_errors() {
+        let error_result: ToolResult<CallToolResult> = Err(ErrorData {
+            code: ErrorCode::INTERNAL_ERROR,
+            message: Cow::from("test error"),
+            data: None,
+        });
+
+        let validated = call_tool_result::validate(error_result.clone());
+
+        assert!(validated.is_err());
+        assert_eq!(validated.unwrap_err().message, "test error");
+    }
 }