Fix empty tool results from resource content (e.g. auto visualiser) (#7866)

Co-authored-by: Douwe Osinga <douwe@squareup.com>

crates/goose/src/providers/formats/anthropic.rs

@@ -1,4 +1,5 @@
 use crate::conversation::message::{Message, MessageContent};
+use crate::mcp_utils::extract_text_from_resource;
 use crate::model::ModelConfig;
 use crate::providers::base::Usage;
 use crate::providers::errors::ProviderError;
@@ -142,7 +143,18 @@ pub fn format_messages(messages: &[Message]) -> Vec<Value> {
                         let text = result
                             .content
                             .iter()
-                            .filter_map(|c| c.as_text().map(|t| t.text.clone()))
+                            .filter_map(|c| {
+                                if let Some(t) = c.as_text() {
+                                    return Some(t.text.clone());
+                                }
+                                if let Some(r) = c.as_resource() {
+                                    let text = extract_text_from_resource(&r.resource);
+                                    if !text.is_empty() {
+                                        return Some(text);
+                                    }
+                                }
+                                None
+                            })
                             .collect::<Vec<_>>()
                             .join("\n");
 
@@ -1170,6 +1182,70 @@ mod tests {
         assert_eq!(assistant_content[0]["type"], "tool_use");
     }
 
+    #[test]
+    fn test_tool_response_with_resource_content() {
+        use rmcp::model::{CallToolResult, Content};
+
+        let resource_content = Content::embedded_text(
+            "file:///test/file.txt",
+            "This is the file content from a resource",
+        );
+
+        let messages = vec![
+            Message::assistant().with_tool_request(
+                "tool_1",
+                Ok(CallToolRequestParams::new("view_file")
+                    .with_arguments(object!({"path": "/test/file.txt"}))),
+            ),
+            Message::user().with_tool_response(
+                "tool_1",
+                Ok(CallToolResult::success(vec![resource_content])),
+            ),
+        ];
+
+        let spec = format_messages(&messages);
+
+        assert_eq!(spec.len(), 2);
+        assert_eq!(spec[1]["role"], "user");
+        assert_eq!(spec[1]["content"][0]["type"], "tool_result");
+        assert_eq!(spec[1]["content"][0]["tool_use_id"], "tool_1");
+        assert_eq!(
+            spec[1]["content"][0]["content"],
+            "This is the file content from a resource"
+        );
+    }
+
+    #[test]
+    fn test_tool_response_with_mixed_content() {
+        use rmcp::model::{CallToolResult, Content};
+
+        let text_content = Content::text("Summary: file loaded");
+        let resource_content = Content::embedded_text("file:///test/file.txt", "File content here");
+
+        let messages = vec![
+            Message::assistant().with_tool_request(
+                "tool_1",
+                Ok(CallToolRequestParams::new("view_file")
+                    .with_arguments(object!({"path": "/test/file.txt"}))),
+            ),
+            Message::user().with_tool_response(
+                "tool_1",
+                Ok(CallToolResult::success(vec![
+                    text_content,
+                    resource_content,
+                ])),
+            ),
+        ];
+
+        let spec = format_messages(&messages);
+
+        assert_eq!(spec[1]["content"][0]["type"], "tool_result");
+        assert_eq!(
+            spec[1]["content"][0]["content"],
+            "Summary: file loaded\nFile content here"
+        );
+    }
+
     fn cfg(name: &str) -> ModelConfig {
         ModelConfig {
             model_name: name.to_string(),

crates/goose/src/providers/formats/snowflake.rs

@@ -1,4 +1,5 @@
 use crate::conversation::message::{Message, MessageContent};
+use crate::mcp_utils::extract_text_from_resource;
 use crate::model::ModelConfig;
 use crate::providers::base::Usage;
 use crate::providers::errors::ProviderError;
@@ -38,7 +39,18 @@ pub fn format_messages(messages: &[Message]) -> Vec<Value> {
                         let text = result
                             .content
                             .iter()
-                            .filter_map(|c| c.as_text().map(|t| t.text.clone()))
+                            .filter_map(|c| {
+                                if let Some(t) = c.as_text() {
+                                    return Some(t.text.clone());
+                                }
+                                if let Some(r) = c.as_resource() {
+                                    let text = extract_text_from_resource(&r.resource);
+                                    if !text.is_empty() {
+                                        return Some(text);
+                                    }
+                                }
+                                None
+                            })
                             .collect::<Vec<_>>()
                             .join("\n");