feat(mcp): upgrade rmcp to 0.15.0 and advertise MCP Apps UI extension capability (#6927)

crates/goose-mcp/src/autovisualiser/mod.rs

@@ -417,6 +417,7 @@ impl ServerHandler for AutoVisualiserRouter {
                 name: "goose-autovisualiser".to_string(),
                 version: env!("CARGO_PKG_VERSION").to_owned(),
                 title: None,
+                description: None,
                 icons: None,
                 website_url: None,
             },

crates/goose-mcp/src/computercontroller/mod.rs

@@ -1301,6 +1301,7 @@ impl ServerHandler for ComputerControllerServer {
                 name: "goose-computercontroller".to_string(),
                 version: env!("CARGO_PKG_VERSION").to_owned(),
                 title: None,
+                description: None,
                 icons: None,
                 website_url: None,
             },

crates/goose-mcp/src/developer/rmcp_developer.rs

@@ -427,6 +427,7 @@ impl ServerHandler for DeveloperServer {
                 name: "goose-developer".to_string(),
                 version: env!("CARGO_PKG_VERSION").to_owned(),
                 title: None,
+                description: None,
                 icons: None,
                 website_url: None,
             },

crates/goose-mcp/src/memory/mod.rs

@@ -549,6 +549,7 @@ impl ServerHandler for MemoryServer {
                 name: "goose-memory".to_string(),
                 version: env!("CARGO_PKG_VERSION").to_owned(),
                 title: None,
+                description: None,
                 icons: None,
                 website_url: None,
             },

crates/goose-mcp/src/tutorial/mod.rs

@@ -114,6 +114,7 @@ impl ServerHandler for TutorialServer {
                 name: "goose-tutorial".to_string(),
                 version: env!("CARGO_PKG_VERSION").to_owned(),
                 title: None,
+                description: None,
                 icons: None,
                 website_url: None,
             },

crates/goose-server/src/openapi.rs

@@ -12,7 +12,7 @@ use goose::session::{Session, SessionInsights, SessionType, SystemInfo};
 use rmcp::model::{
     Annotations, Content, EmbeddedResource, Icon, ImageContent, JsonObject, RawAudioContent,
     RawEmbeddedResource, RawImageContent, RawResource, RawTextContent, ResourceContents, Role,
-    TextContent, Tool, ToolAnnotations,
+    TaskSupport, TextContent, Tool, ToolAnnotations, ToolExecution,
 };
 use utoipa::{OpenApi, ToSchema};
 
@@ -319,6 +319,8 @@ derive_utoipa!(RawEmbeddedResource as RawEmbeddedResourceSchema);
 derive_utoipa!(RawResource as RawResourceSchema);
 derive_utoipa!(Tool as ToolSchema);
 derive_utoipa!(ToolAnnotations as ToolAnnotationsSchema);
+derive_utoipa!(ToolExecution as ToolExecutionSchema);
+derive_utoipa!(TaskSupport as TaskSupportSchema);
 derive_utoipa!(Annotations as AnnotationsSchema);
 derive_utoipa!(ResourceContents as ResourceContentsSchema);
 derive_utoipa!(JsonObject as JsonObjectSchema);
@@ -497,6 +499,8 @@ derive_utoipa!(Icon as IconSchema);
         RecipeManifest,
         ToolSchema,
         ToolAnnotationsSchema,
+        ToolExecutionSchema,
+        TaskSupportSchema,
         ToolInfo,
         PermissionLevel,
         Permission,

crates/goose/src/agents/apps_extension.rs

@@ -131,11 +131,13 @@ impl AppsManagerClient {
                 experimental: None,
                 tasks: None,
                 logging: None,
+                extensions: None,
             },
             server_info: Implementation {
                 name: EXTENSION_NAME.to_string(),
                 title: Some("Apps Manager".to_string()),
                 version: "1.0.0".to_string(),
+                description: None,
                 icons: None,
                 website_url: None,
             },

crates/goose/src/agents/chatrecall_extension.rs

@@ -43,11 +43,12 @@ impl ChatRecallClient {
         let info = InitializeResult {
             protocol_version: ProtocolVersion::V_2025_03_26,
             capabilities: ServerCapabilities {
-                tasks: None,
                 tools: Some(ToolsCapability {
                     list_changed: Some(false),
                 }),
+                tasks: None,
                 resources: None,
+                extensions: None,
                 prompts: None,
                 completions: None,
                 experimental: None,
@@ -55,6 +56,7 @@ impl ChatRecallClient {
             },
             server_info: Implementation {
                 name: EXTENSION_NAME.to_string(),
+                description: None,
                 title: Some("Chat Recall".to_string()),
                 version: "1.0.0".to_string(),
                 icons: None,

crates/goose/src/agents/code_execution_extension.rs

@@ -56,11 +56,12 @@ impl CodeExecutionClient {
         let info = InitializeResult {
             protocol_version: ProtocolVersion::V_2025_03_26,
             capabilities: ServerCapabilities {
-                tasks: None,
                 tools: Some(ToolsCapability {
                     list_changed: Some(false),
                 }),
+                tasks: None,
                 resources: None,
+                extensions: None,
                 prompts: None,
                 completions: None,
                 experimental: None,
@@ -68,6 +69,7 @@ impl CodeExecutionClient {
             },
             server_info: Implementation {
                 name: EXTENSION_NAME.to_string(),
+                description: None,
                 title: Some("Code Mode".to_string()),
                 version: "1.0.0".to_string(),
                 icons: None,

crates/goose/src/agents/extension_manager.rs

@@ -925,6 +925,7 @@ impl ExtensionManager {
                                 input_schema: tool.input_schema,
                                 annotations: tool.annotations,
                                 output_schema: tool.output_schema,
+                                execution: tool.execution,
                                 icons: tool.icons,
                                 title: tool.title,
                                 meta: Some(rmcp::model::Meta(meta_map)),

crates/goose/src/agents/extension_manager_extension.rs

@@ -85,11 +85,12 @@ impl ExtensionManagerClient {
         let info = InitializeResult {
             protocol_version: ProtocolVersion::V_2025_03_26,
             capabilities: ServerCapabilities {
-                tasks: None,
                 tools: Some(ToolsCapability {
                     list_changed: Some(false),
                 }),
+                tasks: None,
                 resources: None,
+                extensions: None,
                 prompts: None,
                 completions: None,
                 experimental: None,
@@ -97,6 +98,7 @@ impl ExtensionManagerClient {
             },
             server_info: Implementation {
                 name: EXTENSION_NAME.to_string(),
+                description: None,
                 title: Some(EXTENSION_NAME.to_string()),
                 version: "1.0.0".to_string(),
                 icons: None,

crates/goose/src/agents/mcp_client.rs

@@ -2,8 +2,8 @@ use crate::action_required_manager::ActionRequiredManager;
 use crate::agents::types::SharedProvider;
 use crate::session_context::{SESSION_ID_HEADER, WORKING_DIR_HEADER};
 use rmcp::model::{
-    Content, CreateElicitationRequestParams, CreateElicitationResult, ElicitationAction, ErrorCode,
-    Extensions, JsonObject, Meta,
+    CreateElicitationRequestParams, CreateElicitationResult, ElicitationAction, ErrorCode,
+    ExtensionCapabilities, Extensions, JsonObject, Meta, SamplingMessageContent,
 };
 /// MCP client implementation for Goose
 use rmcp::{
@@ -223,9 +223,9 @@ impl ClientHandler for GooseClient {
                     Role::Assistant => crate::conversation::message::Message::assistant(),
                 };
 
-                match msg.content.as_text() {
+                match msg.content.first().and_then(|c| c.as_text()) {
                     Some(text) => base.with_text(&text.text),
-                    None => base.with_content(msg.content.clone().into()),
+                    None => base,
                 }
             })
             .collect();
@@ -255,29 +255,26 @@ impl ClientHandler for GooseClient {
         Ok(CreateMessageResult {
             model: usage.model,
             stop_reason: Some(CreateMessageResult::STOP_REASON_END_TURN.to_string()),
-            message: SamplingMessage {
-                role: Role::Assistant,
-                // TODO(alexhancock): MCP sampling currently only supports one content on each SamplingMessage
-                // https://modelcontextprotocol.io/specification/draft/client/sampling#messages
-                // This doesn't mesh well with goose's approach which has Vec<MessageContent>
-                // There is a proposal to MCP which is agreed to go in the next version to have SamplingMessages support multiple content parts
-                // https://github.com/modelcontextprotocol/modelcontextprotocol/pull/198
-                // Until that is formalized, we can take the first message content from the provider and use it
-                content: if let Some(content) = response.content.first() {
+            message: SamplingMessage::new(
+                Role::Assistant,
+                if let Some(content) = response.content.first() {
                     match content {
                         crate::conversation::message::MessageContent::Text(text) => {
-                            Content::text(&text.text)
+                            SamplingMessageContent::text(&text.text)
                         }
                         crate::conversation::message::MessageContent::Image(img) => {
-                            Content::image(&img.data, &img.mime_type)
+                            SamplingMessageContent::Image(rmcp::model::RawImageContent {
+                                data: img.data.clone(),
+                                mime_type: img.mime_type.clone(),
+                                meta: None,
+                            })
                         }
-                        // TODO(alexhancock) - Content::Audio? goose's messages don't currently have it
-                        _ => Content::text(""),
+                        _ => SamplingMessageContent::text(""),
                     }
                 } else {
-                    Content::text("")
+                    SamplingMessageContent::text("")
                 },
-            },
+            ),
         })
     }
 
@@ -286,20 +283,28 @@ impl ClientHandler for GooseClient {
         request: CreateElicitationRequestParams,
         _context: RequestContext<RoleClient>,
     ) -> Result<CreateElicitationResult, ErrorData> {
-        let schema_value = serde_json::to_value(&request.requested_schema).map_err(|e| {
-            ErrorData::new(
-                ErrorCode::INTERNAL_ERROR,
-                format!("Failed to serialize elicitation schema: {}", e),
-                None,
-            )
-        })?;
+        let (message, schema_value) = match &request {
+            CreateElicitationRequestParams::FormElicitationParams {
+                message,
+                requested_schema,
+                ..
+            } => {
+                let schema_value = serde_json::to_value(requested_schema).map_err(|e| {
+                    ErrorData::new(
+                        ErrorCode::INTERNAL_ERROR,
+                        format!("Failed to serialize elicitation schema: {}", e),
+                        None,
+                    )
+                })?;
+                (message.clone(), schema_value)
+            }
+            CreateElicitationRequestParams::UrlElicitationParams { message, url, .. } => {
+                (message.clone(), serde_json::json!({ "url": url }))
+            }
+        };
 
         ActionRequiredManager::global()
-            .request_and_wait(
-                request.message.clone(),
-                schema_value,
-                Duration::from_secs(300),
-            )
+            .request_and_wait(message, schema_value, Duration::from_secs(300))
             .await
             .map(|user_data| CreateElicitationResult {
                 action: ElicitationAction::Accept,
@@ -315,10 +320,25 @@ impl ClientHandler for GooseClient {
     }
 
     fn get_info(&self) -> ClientInfo {
+        // Build MCP Apps UI extension capability
+        // See: https://github.com/modelcontextprotocol/ext-apps/blob/main/specification/2026-01-26/apps.mdx
+        let mut ui_extension_settings = JsonObject::new();
+        ui_extension_settings.insert(
+            "mimeTypes".to_string(),
+            serde_json::json!(["text/html;profile=mcp-app"]),
+        );
+
+        let mut extensions = ExtensionCapabilities::new();
+        extensions.insert(
+            "io.modelcontextprotocol/ui".to_string(),
+            ui_extension_settings,
+        );
+
         ClientInfo {
             meta: None,
             protocol_version: ProtocolVersion::V_2025_03_26,
             capabilities: ClientCapabilities::builder()
+                .enable_extensions_with(extensions)
                 .enable_sampling()
                 .enable_elicitation()
                 .build(),
@@ -328,6 +348,7 @@ impl ClientHandler for GooseClient {
                     .unwrap_or(env!("CARGO_PKG_VERSION").to_owned()),
                 icons: None,
                 title: None,
+                description: None,
                 website_url: None,
             },
         }
@@ -945,4 +966,26 @@ mod tests {
 
         assert_eq!(&mcp_meta.0, expected_meta.as_object().unwrap());
     }
+
+    #[test]
+    fn test_client_info_advertises_mcp_apps_ui_extension() {
+        let client = new_client();
+        let info = ClientHandler::get_info(&client);
+
+        // Verify the client advertises the MCP Apps UI extension capability
+        let extensions = info
+            .capabilities
+            .extensions
+            .expect("capabilities should have extensions");
+
+        let ui_ext = extensions
+            .get("io.modelcontextprotocol/ui")
+            .expect("should have io.modelcontextprotocol/ui extension");
+
+        let mime_types = ui_ext
+            .get("mimeTypes")
+            .expect("ui extension should have mimeTypes");
+
+        assert_eq!(mime_types, &json!(["text/html;profile=mcp-app"]));
+    }
 }

crates/goose/src/agents/summon_extension.rs

@@ -260,11 +260,13 @@ impl SummonClient {
                 completions: None,
                 experimental: None,
                 logging: None,
+                extensions: None,
             },
             server_info: Implementation {
                 name: EXTENSION_NAME.to_string(),
                 title: Some("Summon".to_string()),
                 version: "1.0.0".to_string(),
+                description: None,
                 icons: None,
                 website_url: None,
             },

crates/goose/src/agents/todo_extension.rs

@@ -30,11 +30,12 @@ impl TodoClient {
         let info = InitializeResult {
             protocol_version: ProtocolVersion::V_2025_03_26,
             capabilities: ServerCapabilities {
-                tasks: None,
                 tools: Some(ToolsCapability {
                     list_changed: Some(false),
                 }),
+                tasks: None,
                 resources: None,
+                extensions: None,
                 prompts: None,
                 completions: None,
                 experimental: None,
@@ -42,6 +43,7 @@ impl TodoClient {
             },
             server_info: Implementation {
                 name: EXTENSION_NAME.to_string(),
+                description: None,
                 title: Some("Todo".to_string()),
                 version: "1.0.0".to_string(),
                 icons: None,

crates/goose/src/agents/tom_extension.rs

@@ -30,11 +30,13 @@ impl TomClient {
                     completions: None,
                     experimental: None,
                     logging: None,
+                    extensions: None,
                 },
                 server_info: Implementation {
                     name: EXTENSION_NAME.to_string(),
                     title: Some("Top Of Mind".to_string()),
                     version: "1.0.0".to_string(),
+                    description: None,
                     icons: None,
                     website_url: None,
                 },

crates/goose/tests/mcp_replays/github-mcp-serverstdio

@@ -1,4 +1,4 @@
-STDIN: {"jsonrpc":"2.0","id":0,"method":"initialize","params":{"protocolVersion":"2025-03-26","capabilities":{"sampling":{},"elicitation":{}},"clientInfo":{"name":"goose","version":"0.0.0"}}}
+STDIN: {"jsonrpc":"2.0","id":0,"method":"initialize","params":{"protocolVersion":"2025-03-26","capabilities":{"elicitation":{},"extensions":{"io.modelcontextprotocol/ui":{"mimeTypes":["text/html;profile=mcp-app"]}},"sampling":{}},"clientInfo":{"name":"goose","version":"0.0.0"}}}
 STDERR: time=2025-12-11T17:58:47.636-05:00 level=INFO msg="starting server" version=0.24.1 host="" dynamicToolsets=false readOnly=false lockdownEnabled=false
 STDERR: GitHub MCP Server running on stdio
 STDERR: time=2025-12-11T17:58:47.640-05:00 level=INFO msg="server run start"

crates/goose/tests/mcp_replays/npx-y@modelcontextprotocol_server-everything@2026.1.14

@@ -1,4 +1,4 @@
-STDIN: {"jsonrpc":"2.0","id":0,"method":"initialize","params":{"protocolVersion":"2025-03-26","capabilities":{"sampling":{},"elicitation":{}},"clientInfo":{"name":"goose","version":"0.0.0"}}}
+STDIN: {"jsonrpc":"2.0","id":0,"method":"initialize","params":{"protocolVersion":"2025-03-26","capabilities":{"elicitation":{},"extensions":{"io.modelcontextprotocol/ui":{"mimeTypes":["text/html;profile=mcp-app"]}},"sampling":{}},"clientInfo":{"name":"goose","version":"0.0.0"}}}
 STDERR: Starting default (STDIO) server...
 STDOUT: {"result":{"protocolVersion":"2025-03-26","capabilities":{"tools":{"listChanged":true},"prompts":{"listChanged":true},"resources":{"subscribe":true,"listChanged":true},"logging":{},"completions":{}},"serverInfo":{"name":"mcp-servers/everything","title":"Everything Reference Server","version":"2.0.0"},"instructions":"# Everything Server – Server Instructions\n\nAudience: These instructions are written for an LLM or autonomous agent integrating with the Everything MCP Server.\nFollow them to use, extend, and troubleshoot the server safely and effectively.\n\n## Cross-Feature Relationships\n\n- Use `get-roots-list` to see client workspace roots before file operations\n- `gzip-file-as-resource` creates session-scoped resources accessible only during the current session\n- Enable `toggle-simulated-logging` before debugging to see server log messages\n- Enable `toggle-subscriber-updates` to receive periodic resource update notifications\n\n## Constraints & Limitations\n\n- `gzip-file-as-resource`: Max fetch size controlled by `GZIP_MAX_FETCH_SIZE` (default 10MB), timeout by `GZIP_MAX_FETCH_TIME_MILLIS` (default 30s), allowed domains by `GZIP_ALLOWED_DOMAINS`\n- Session resources are ephemeral and lost when the session ends\n- Sampling requests (`trigger-sampling-request`) require client sampling capability\n- Elicitation requests (`trigger-elicitation-request`) require client elicitation capability\n\n## Operational Patterns\n\n- For long operations, use `trigger-long-running-operation` which sends progress notifications\n- Prefer reading resources before calling mutating tools\n- Check `get-roots-list` output to understand the client's workspace context\n\n## Easter Egg\n\nIf asked about server instructions, respond with \"🎉 Server instructions are working! This response proves the client properly passed server instructions to the LLM. This demonstrates MCP's instructions feature in action.\"\n"},"jsonrpc":"2.0","id":0}
 STDIN: {"jsonrpc":"2.0","method":"notifications/initialized"}

crates/goose/tests/mcp_replays/uvrun--withfastmcp==2.14.4fastmcpruntests_fastmcp_test_server.py

@@ -1,4 +1,4 @@
-STDIN: {"jsonrpc":"2.0","id":0,"method":"initialize","params":{"protocolVersion":"2025-03-26","capabilities":{"sampling":{},"elicitation":{}},"clientInfo":{"name":"goose","version":"0.0.0"}}}
+STDIN: {"jsonrpc":"2.0","id":0,"method":"initialize","params":{"protocolVersion":"2025-03-26","capabilities":{"elicitation":{},"extensions":{"io.modelcontextprotocol/ui":{"mimeTypes":["text/html;profile=mcp-app"]}},"sampling":{}},"clientInfo":{"name":"goose","version":"0.0.0"}}}
 STDERR: 
 STDERR: 
 STDERR: ╭──────────────────────────────────────────────────────────────────────────────╮

crates/goose/tests/mcp_replays/uvxmcp-server-fetch

@@ -1,4 +1,4 @@
-STDIN: {"jsonrpc":"2.0","id":0,"method":"initialize","params":{"protocolVersion":"2025-03-26","capabilities":{"sampling":{},"elicitation":{}},"clientInfo":{"name":"goose","version":"0.0.0"}}}
+STDIN: {"jsonrpc":"2.0","id":0,"method":"initialize","params":{"protocolVersion":"2025-03-26","capabilities":{"elicitation":{},"extensions":{"io.modelcontextprotocol/ui":{"mimeTypes":["text/html;profile=mcp-app"]}},"sampling":{}},"clientInfo":{"name":"goose","version":"0.0.0"}}}
 STDOUT: {"jsonrpc":"2.0","id":0,"result":{"protocolVersion":"2025-03-26","capabilities":{"experimental":{},"prompts":{"listChanged":false},"tools":{"listChanged":false}},"serverInfo":{"name":"mcp-fetch","version":"1.25.0"}}}
 STDIN: {"jsonrpc":"2.0","method":"notifications/initialized"}
 STDIN: {"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"_meta":{"agent-session-id":"test-session-id","progressToken":0},"name":"fetch","arguments":{"url":"https://example.com"}}}