Context Servers: Protocol fixes and UI improvements (#19087)

This PR does two things. It fixes some minor inconsistencies in the
protocol. This is mostly about handling JSON RPC notifications correctly
and skipping fields when set to None.

Second part is about improving the rendering of context server commands,
by passing on the description
of the command to the slash command UI and showing the name of the
argument as a CodeLabel.

Release Notes:

- N/A

crates/assistant/src/slash_command/context_server_command.rs

@@ -1,3 +1,4 @@
+use super::create_label_for_command;
 use anyhow::{anyhow, Result};
 use assistant_slash_command::{
     AfterCompletion, ArgumentCompletion, SlashCommand, SlashCommandOutput,
@@ -6,9 +7,9 @@ use assistant_slash_command::{
 use collections::HashMap;
 use context_servers::{
     manager::{ContextServer, ContextServerManager},
-    protocol::PromptInfo,
+    types::Prompt,
 };
-use gpui::{Task, WeakView, WindowContext};
+use gpui::{AppContext, Task, WeakView, WindowContext};
 use language::{BufferSnapshot, CodeLabel, LspAdapterDelegate};
 use std::sync::atomic::AtomicBool;
 use std::sync::Arc;
@@ -18,11 +19,11 @@ use workspace::Workspace;
 
 pub struct ContextServerSlashCommand {
     server_id: String,
-    prompt: PromptInfo,
+    prompt: Prompt,
 }
 
 impl ContextServerSlashCommand {
-    pub fn new(server: &Arc<ContextServer>, prompt: PromptInfo) -> Self {
+    pub fn new(server: &Arc<ContextServer>, prompt: Prompt) -> Self {
         Self {
             server_id: server.id.clone(),
             prompt,
@@ -35,12 +36,28 @@ impl SlashCommand for ContextServerSlashCommand {
         self.prompt.name.clone()
     }
 
+    fn label(&self, cx: &AppContext) -> language::CodeLabel {
+        let mut parts = vec![self.prompt.name.as_str()];
+        if let Some(args) = &self.prompt.arguments {
+            if let Some(arg) = args.first() {
+                parts.push(arg.name.as_str());
+            }
+        }
+        create_label_for_command(&parts[0], &parts[1..], cx)
+    }
+
     fn description(&self) -> String {
-        format!("Run context server command: {}", self.prompt.name)
+        match &self.prompt.description {
+            Some(desc) => desc.clone(),
+            None => format!("Run '{}' from {}", self.prompt.name, self.server_id),
+        }
     }
 
     fn menu_text(&self) -> String {
-        format!("Run '{}' from {}", self.prompt.name, self.server_id)
+        match &self.prompt.description {
+            Some(desc) => desc.clone(),
+            None => format!("Run '{}' from {}", self.prompt.name, self.server_id),
+        }
     }
 
     fn requires_argument(&self) -> bool {
@@ -154,7 +171,7 @@ impl SlashCommand for ContextServerSlashCommand {
     }
 }
 
-fn completion_argument(prompt: &PromptInfo, arguments: &[String]) -> Result<(String, String)> {
+fn completion_argument(prompt: &Prompt, arguments: &[String]) -> Result<(String, String)> {
     if arguments.is_empty() {
         return Err(anyhow!("No arguments given"));
     }
@@ -170,7 +187,7 @@ fn completion_argument(prompt: &PromptInfo, arguments: &[String]) -> Result<(Str
     }
 }
 
-fn prompt_arguments(prompt: &PromptInfo, arguments: &[String]) -> Result<HashMap<String, String>> {
+fn prompt_arguments(prompt: &Prompt, arguments: &[String]) -> Result<HashMap<String, String>> {
     match &prompt.arguments {
         Some(args) if args.len() > 1 => Err(anyhow!(
             "Prompt has more than one argument, which is not supported"
@@ -199,7 +216,7 @@ fn prompt_arguments(prompt: &PromptInfo, arguments: &[String]) -> Result<HashMap
 /// MCP servers can return prompts with multiple arguments. Since we only
 /// support one argument, we ignore all others. This is the necessary predicate
 /// for this.
-pub fn acceptable_prompt(prompt: &PromptInfo) -> bool {
+pub fn acceptable_prompt(prompt: &Prompt) -> bool {
     match &prompt.arguments {
         None => true,
         Some(args) if args.len() <= 1 => true,

crates/context_servers/src/client.rs

@@ -26,7 +26,7 @@ const JSON_RPC_VERSION: &str = "2.0";
 const REQUEST_TIMEOUT: Duration = Duration::from_secs(60);
 
 type ResponseHandler = Box<dyn Send + FnOnce(Result<String, Error>)>;
-type NotificationHandler = Box<dyn Send + FnMut(RequestId, Value, AsyncAppContext)>;
+type NotificationHandler = Box<dyn Send + FnMut(Value, AsyncAppContext)>;
 
 #[derive(Debug, Clone, Eq, PartialEq, Hash, Serialize, Deserialize)]
 #[serde(untagged)]
@@ -94,7 +94,6 @@ enum CspResult<T> {
 #[derive(Serialize, Deserialize)]
 struct Notification<'a, T> {
     jsonrpc: &'static str,
-    id: RequestId,
     #[serde(borrow)]
     method: &'a str,
     params: T,
@@ -103,7 +102,6 @@ struct Notification<'a, T> {
 #[derive(Debug, Clone, Deserialize)]
 struct AnyNotification<'a> {
     jsonrpc: &'a str,
-    id: RequestId,
     method: String,
     #[serde(default)]
     params: Option<Value>,
@@ -246,11 +244,7 @@ impl Client {
                     if let Some(handler) =
                         notification_handlers.get_mut(notification.method.as_str())
                     {
-                        handler(
+                        handler(notification.params.unwrap_or(Value::Null), cx.clone());
-                            notification.id,
-                            notification.params.unwrap_or(Value::Null),
-                            cx.clone(),
-                        );
                     }
                 }
             }
@@ -378,10 +372,8 @@ impl Client {
     /// Sends a notification to the context server without expecting a response.
     /// This function serializes the notification and sends it through the outbound channel.
     pub fn notify(&self, method: &str, params: impl Serialize) -> Result<()> {
-        let id = self.next_id.fetch_add(1, SeqCst);
         let notification = serde_json::to_string(&Notification {
             jsonrpc: JSON_RPC_VERSION,
-            id: RequestId::Int(id),
             method,
             params,
         })
@@ -390,13 +382,13 @@ impl Client {
         Ok(())
     }
 
-    pub fn on_notification<F>(&self, method: &'static str, mut f: F)
+    pub fn on_notification<F>(&self, method: &'static str, f: F)
     where
         F: 'static + Send + FnMut(Value, AsyncAppContext),
     {
         self.notification_handlers
             .lock()
-            .insert(method, Box::new(move |_, params, cx| f(params, cx)));
+            .insert(method, Box::new(f));
     }
 
     pub fn name(&self) -> &str {

crates/context_servers/src/manager.rs

@@ -85,7 +85,7 @@ impl ContextServer {
         )?;
 
         let protocol = crate::protocol::ModelContextProtocol::new(client);
-        let client_info = types::EntityInfo {
+        let client_info = types::Implementation {
             name: "Zed".to_string(),
             version: env!("CARGO_PKG_VERSION").to_string(),
         };

crates/context_servers/src/protocol.rs

@@ -11,8 +11,6 @@ use collections::HashMap;
 use crate::client::Client;
 use crate::types;
 
-pub use types::PromptInfo;
-
 const PROTOCOL_VERSION: u32 = 1;
 
 pub struct ModelContextProtocol {
@@ -26,7 +24,7 @@ impl ModelContextProtocol {
 
     pub async fn initialize(
         self,
-        client_info: types::EntityInfo,
+        client_info: types::Implementation,
     ) -> Result<InitializedContextServerProtocol> {
         let params = types::InitializeParams {
             protocol_version: PROTOCOL_VERSION,
@@ -96,7 +94,7 @@ impl InitializedContextServerProtocol {
     }
 
     /// List the MCP prompts.
-    pub async fn list_prompts(&self) -> Result<Vec<types::PromptInfo>> {
+    pub async fn list_prompts(&self) -> Result<Vec<types::Prompt>> {
         self.check_capability(ServerCapability::Prompts)?;
 
         let response: types::PromptsListResponse = self
@@ -107,6 +105,18 @@ impl InitializedContextServerProtocol {
         Ok(response.prompts)
     }
 
+    /// List the MCP resources.
+    pub async fn list_resources(&self) -> Result<types::ResourcesListResponse> {
+        self.check_capability(ServerCapability::Resources)?;
+
+        let response: types::ResourcesListResponse = self
+            .inner
+            .request(types::RequestType::ResourcesList.as_str(), ())
+            .await?;
+
+        Ok(response)
+    }
+
     /// Executes a prompt with the given arguments and returns the result.
     pub async fn run_prompt<P: AsRef<str>>(
         &self,

crates/context_servers/src/types.rs

@@ -15,6 +15,7 @@ pub enum RequestType {
     PromptsGet,
     PromptsList,
     CompletionComplete,
+    Ping,
 }
 
 impl RequestType {
@@ -30,6 +31,7 @@ impl RequestType {
             RequestType::PromptsGet => "prompts/get",
             RequestType::PromptsList => "prompts/list",
             RequestType::CompletionComplete => "completion/complete",
+            RequestType::Ping => "ping",
         }
     }
 }
@@ -39,14 +41,15 @@ impl RequestType {
 pub struct InitializeParams {
     pub protocol_version: u32,
     pub capabilities: ClientCapabilities,
-    pub client_info: EntityInfo,
+    pub client_info: Implementation,
 }
 
 #[derive(Debug, Serialize)]
 #[serde(rename_all = "camelCase")]
 pub struct CallToolParams {
     pub name: String,
-    pub arguments: Option<serde_json::Value>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub arguments: Option<HashMap<String, serde_json::Value>>,
 }
 
 #[derive(Debug, Serialize)]
@@ -77,6 +80,7 @@ pub struct LoggingSetLevelParams {
 #[serde(rename_all = "camelCase")]
 pub struct PromptsGetParams {
     pub name: String,
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub arguments: Option<HashMap<String, String>>,
 }
 
@@ -101,6 +105,13 @@ pub struct PromptReference {
     pub name: String,
 }
 
+#[derive(Debug, Serialize)]
+#[serde(rename_all = "camelCase")]
+pub struct ResourceReference {
+    pub r#type: PromptReferenceType,
+    pub uri: Url,
+}
+
 #[derive(Debug, Serialize)]
 #[serde(rename_all = "snake_case")]
 pub enum PromptReferenceType {
@@ -110,13 +121,6 @@ pub enum PromptReferenceType {
     Resource,
 }
 
-#[derive(Debug, Serialize)]
-#[serde(rename_all = "camelCase")]
-pub struct ResourceReference {
-    pub r#type: String,
-    pub uri: String,
-}
-
 #[derive(Debug, Serialize)]
 #[serde(rename_all = "camelCase")]
 pub struct CompletionArgument {
@@ -129,7 +133,7 @@ pub struct CompletionArgument {
 pub struct InitializeResponse {
     pub protocol_version: u32,
     pub capabilities: ServerCapabilities,
-    pub server_info: EntityInfo,
+    pub server_info: Implementation,
 }
 
 #[derive(Debug, Deserialize)]
@@ -141,13 +145,39 @@ pub struct ResourcesReadResponse {
 #[derive(Debug, Deserialize)]
 #[serde(rename_all = "camelCase")]
 pub struct ResourcesListResponse {
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub resource_templates: Option<Vec<ResourceTemplate>>,
-    pub resources: Vec<Resource>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub resources: Option<Vec<Resource>>,
+}
+
+#[derive(Debug, Serialize, Deserialize)]
+#[serde(rename_all = "camelCase")]
+pub struct SamplingMessage {
+    pub role: SamplingRole,
+    pub content: SamplingContent,
+}
+
+#[derive(Debug, Serialize, Deserialize)]
+#[serde(rename_all = "lowercase")]
+pub enum SamplingRole {
+    User,
+    Assistant,
+}
+
+#[derive(Debug, Serialize, Deserialize)]
+#[serde(tag = "type")]
+pub enum SamplingContent {
+    #[serde(rename = "text")]
+    Text { text: String },
+    #[serde(rename = "image")]
+    Image { data: String, mime_type: String },
 }
 
 #[derive(Debug, Deserialize)]
 #[serde(rename_all = "camelCase")]
 pub struct PromptsGetResponse {
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub description: Option<String>,
     pub prompt: String,
 }
@@ -155,7 +185,7 @@ pub struct PromptsGetResponse {
 #[derive(Debug, Deserialize)]
 #[serde(rename_all = "camelCase")]
 pub struct PromptsListResponse {
-    pub prompts: Vec<PromptInfo>,
+    pub prompts: Vec<Prompt>,
 }
 
 #[derive(Debug, Deserialize)]
@@ -168,61 +198,91 @@ pub struct CompletionCompleteResponse {
 #[serde(rename_all = "camelCase")]
 pub struct CompletionResult {
     pub values: Vec<String>,
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub total: Option<u32>,
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub has_more: Option<bool>,
 }
 
-#[derive(Debug, Deserialize, Clone)]
+#[derive(Debug, Deserialize, Serialize)]
 #[serde(rename_all = "camelCase")]
-pub struct PromptInfo {
+pub struct Prompt {
     pub name: String,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub description: Option<String>,
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub arguments: Option<Vec<PromptArgument>>,
 }
 
-#[derive(Debug, Deserialize, Clone)]
+#[derive(Debug, Deserialize, Serialize)]
 #[serde(rename_all = "camelCase")]
 pub struct PromptArgument {
     pub name: String,
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub description: Option<String>,
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub required: Option<bool>,
 }
 
-// Shared Types
-
 #[derive(Debug, Serialize, Deserialize)]
 #[serde(rename_all = "camelCase")]
 pub struct ClientCapabilities {
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub experimental: Option<HashMap<String, serde_json::Value>>,
-    pub sampling: Option<HashMap<String, serde_json::Value>>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub sampling: Option<serde_json::Value>,
 }
 
 #[derive(Debug, Serialize, Deserialize)]
 #[serde(rename_all = "camelCase")]
 pub struct ServerCapabilities {
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub experimental: Option<HashMap<String, serde_json::Value>>,
-    pub logging: Option<HashMap<String, serde_json::Value>>,
+    #[serde(skip_serializing_if = "Option::is_none")]
-    pub prompts: Option<HashMap<String, serde_json::Value>>,
+    pub logging: Option<serde_json::Value>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub prompts: Option<PromptsCapabilities>,
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub resources: Option<ResourcesCapabilities>,
-    pub tools: Option<HashMap<String, serde_json::Value>>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub tools: Option<ToolsCapabilities>,
+}
+
+#[derive(Debug, Serialize, Deserialize)]
+#[serde(rename_all = "camelCase")]
+pub struct PromptsCapabilities {
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub list_changed: Option<bool>,
 }
 
 #[derive(Debug, Serialize, Deserialize)]
 #[serde(rename_all = "camelCase")]
 pub struct ResourcesCapabilities {
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub subscribe: Option<bool>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub list_changed: Option<bool>,
+}
+
+#[derive(Debug, Serialize, Deserialize)]
+#[serde(rename_all = "camelCase")]
+pub struct ToolsCapabilities {
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub list_changed: Option<bool>,
 }
 
 #[derive(Debug, Serialize, Deserialize)]
 #[serde(rename_all = "camelCase")]
 pub struct Tool {
     pub name: String,
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub description: Option<String>,
     pub input_schema: serde_json::Value,
 }
 
 #[derive(Debug, Serialize, Deserialize)]
 #[serde(rename_all = "camelCase")]
-pub struct EntityInfo {
+pub struct Implementation {
     pub name: String,
     pub version: String,
 }
@@ -231,6 +291,10 @@ pub struct EntityInfo {
 #[serde(rename_all = "camelCase")]
 pub struct Resource {
     pub uri: Url,
+    pub name: String,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub description: Option<String>,
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub mime_type: Option<String>,
 }
 
@@ -238,17 +302,23 @@ pub struct Resource {
 #[serde(rename_all = "camelCase")]
 pub struct ResourceContent {
     pub uri: Url,
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub mime_type: Option<String>,
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub text: Option<String>,
-    pub data: Option<String>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub blob: Option<String>,
 }
 
 #[derive(Debug, Serialize, Deserialize)]
 #[serde(rename_all = "camelCase")]
 pub struct ResourceTemplate {
     pub uri_template: String,
-    pub name: Option<String>,
+    pub name: String,
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub description: Option<String>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub mime_type: Option<String>,
 }
 
 #[derive(Debug, Serialize, Deserialize)]
@@ -260,13 +330,16 @@ pub enum LoggingLevel {
     Error,
 }
 
-// Client Notifications
-
 #[derive(Debug, Serialize)]
 #[serde(rename_all = "camelCase")]
 pub enum NotificationType {
     Initialized,
     Progress,
+    Message,
+    ResourcesUpdated,
+    ResourcesListChanged,
+    ToolsListChanged,
+    PromptsListChanged,
 }
 
 impl NotificationType {
@@ -274,6 +347,11 @@ impl NotificationType {
         match self {
             NotificationType::Initialized => "notifications/initialized",
             NotificationType::Progress => "notifications/progress",
+            NotificationType::Message => "notifications/message",
+            NotificationType::ResourcesUpdated => "notifications/resources/updated",
+            NotificationType::ResourcesListChanged => "notifications/resources/list_changed",
+            NotificationType::ToolsListChanged => "notifications/tools/list_changed",
+            NotificationType::PromptsListChanged => "notifications/prompts/list_changed",
         }
     }
 }
@@ -288,12 +366,13 @@ pub enum ClientNotification {
 #[derive(Debug, Serialize)]
 #[serde(rename_all = "camelCase")]
 pub struct ProgressParams {
-    pub progress_token: String,
+    pub progress_token: ProgressToken,
     pub progress: f64,
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub total: Option<f64>,
 }
 
-// Helper Types that don't map directly to the protocol
+pub type ProgressToken = String;
 
 pub enum CompletionTotal {
     Exact(u32),