feat: add prompts support to mcp-client, ahere to MCP spec for prompts

- add new endpoints `list_prompts` and `get_prompt` in the MCP client
- update prompt model in mcp-core to make `description` and `arguments`
  optional, following MCP spec

crates/mcp-client/src/client.rs

@@ -1,7 +1,7 @@
 use mcp_core::protocol::{
-    CallToolResult, Implementation, InitializeResult, JsonRpcError, JsonRpcMessage,
-    JsonRpcNotification, JsonRpcRequest, JsonRpcResponse, ListResourcesResult, ListToolsResult,
-    ReadResourceResult, ServerCapabilities, METHOD_NOT_FOUND,
+    CallToolResult, GetPromptResult, Implementation, InitializeResult, JsonRpcError,
+    JsonRpcMessage, JsonRpcNotification, JsonRpcRequest, JsonRpcResponse, ListPromptsResult,
+    ListResourcesResult, ListToolsResult, ReadResourceResult, ServerCapabilities, METHOD_NOT_FOUND,
 };
 use serde::{Deserialize, Serialize};
 use serde_json::Value;
@@ -93,6 +93,10 @@ pub trait McpClientTrait: Send + Sync {
     async fn list_tools(&self, next_cursor: Option<String>) -> Result<ListToolsResult, Error>;
 
     async fn call_tool(&self, name: &str, arguments: Value) -> Result<CallToolResult, Error>;
+
+    async fn list_prompts(&self, next_cursor: Option<String>) -> Result<ListPromptsResult, Error>;
+
+    async fn get_prompt(&self, name: &str, arguments: Value) -> Result<GetPromptResult, Error>;
 }
 
 /// The MCP client is the interface for MCP operations.
@@ -346,4 +350,42 @@ where
         // https://modelcontextprotocol.io/docs/concepts/tools#error-handling-2
         self.send_request("tools/call", params).await
     }
+
+    async fn list_prompts(&self, next_cursor: Option<String>) -> Result<ListPromptsResult, Error> {
+        if !self.completed_initialization() {
+            return Err(Error::NotInitialized);
+        }
+
+        // If prompts is not supported, return an error
+        if self.server_capabilities.as_ref().unwrap().prompts.is_none() {
+            return Err(Error::RpcError {
+                code: METHOD_NOT_FOUND,
+                message: "Server does not support 'prompts' capability".to_string(),
+            });
+        }
+
+        let payload = next_cursor
+            .map(|cursor| serde_json::json!({"cursor": cursor}))
+            .unwrap_or_else(|| serde_json::json!({}));
+
+        self.send_request("prompts/list", payload).await
+    }
+
+    async fn get_prompt(&self, name: &str, arguments: Value) -> Result<GetPromptResult, Error> {
+        if !self.completed_initialization() {
+            return Err(Error::NotInitialized);
+        }
+
+        // If prompts is not supported, return an error
+        if self.server_capabilities.as_ref().unwrap().prompts.is_none() {
+            return Err(Error::RpcError {
+                code: METHOD_NOT_FOUND,
+                message: "Server does not support 'prompts' capability".to_string(),
+            });
+        }
+
+        let params = serde_json::json!({ "name": name, "arguments": arguments });
+
+        self.send_request("prompts/get", params).await
+    }
 }

crates/mcp-core/src/prompt.rs

@@ -10,22 +10,28 @@ use serde::{Deserialize, Serialize};
 pub struct Prompt {
     /// The name of the prompt
     pub name: String,
-    /// A description of what the prompt does
-    pub description: String,
-    /// The arguments that can be passed to customize the prompt
-    pub arguments: Vec<PromptArgument>,
+    /// Optional description of what the prompt does
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub description: Option<String>,
+    /// Optional arguments that can be passed to customize the prompt
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub arguments: Option<Vec<PromptArgument>>,
 }
 
 impl Prompt {
     /// Create a new prompt with the given name, description and arguments
-    pub fn new<N, D>(name: N, description: D, arguments: Vec<PromptArgument>) -> Self
+    pub fn new<N, D>(
+        name: N,
+        description: Option<D>,
+        arguments: Option<Vec<PromptArgument>>,
+    ) -> Self
     where
         N: Into<String>,
         D: Into<String>,
     {
         Prompt {
             name: name.into(),
-            description: description.into(),
+            description: description.map(Into::into),
             arguments,
         }
     }
@@ -37,9 +43,11 @@ pub struct PromptArgument {
     /// The name of the argument
     pub name: String,
     /// A description of what the argument is used for
-    pub description: String,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub description: Option<String>,
     /// Whether this argument is required
-    pub required: bool,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub required: Option<bool>,
 }
 
 /// Represents the role of a message sender in a prompt conversation
@@ -151,6 +159,6 @@ pub struct PromptTemplate {
 #[derive(Debug, Serialize, Deserialize)]
 pub struct PromptArgumentTemplate {
     pub name: String,
-    pub description: String,
-    pub required: bool,
+    pub description: Option<String>,
+    pub required: Option<bool>,
 }

crates/mcp-server/src/router.rs

@@ -305,18 +305,21 @@ pub trait Router: Send + Sync + 'static {
             };
 
             // Validate required arguments
-            for arg in &prompt.arguments {
-                if arg.required
-                    && (!arguments.contains_key(&arg.name)
-                        || arguments
-                            .get(&arg.name)
-                            .and_then(Value::as_str)
-                            .is_none_or(str::is_empty))
-                {
-                    return Err(RouterError::InvalidParams(format!(
-                        "Missing required argument: '{}'",
-                        arg.name
-                    )));
+            if let Some(args) = &prompt.arguments {
+                for arg in args {
+                    if arg.required.is_some()
+                        && arg.required.unwrap()
+                        && (!arguments.contains_key(&arg.name)
+                            || arguments
+                                .get(&arg.name)
+                                .and_then(Value::as_str)
+                                .is_none_or(str::is_empty))
+                    {
+                        return Err(RouterError::InvalidParams(format!(
+                            "Missing required argument: '{}'",
+                            arg.name
+                        )));
+                    }
                 }
             }