feat(cli): add mcp prompt support via slash commands (#1323)

crates/mcp-server/src/main.rs

@@ -1,6 +1,7 @@
 use anyhow::Result;
 use mcp_core::content::Content;
-use mcp_core::handler::ResourceError;
+use mcp_core::handler::{PromptError, ResourceError};
+use mcp_core::prompt::{Prompt, PromptArgument};
 use mcp_core::{handler::ToolError, protocol::ServerCapabilities, resource::Resource, tool::Tool};
 use mcp_server::router::{CapabilitiesBuilder, RouterService};
 use mcp_server::{ByteTransport, Router, Server};
@@ -61,6 +62,7 @@ impl Router for CounterRouter {
         CapabilitiesBuilder::new()
             .with_tools(false)
             .with_resources(false, false)
+            .with_prompts(false)
             .build()
     }
 
@@ -153,6 +155,37 @@ impl Router for CounterRouter {
             }
         })
     }
+
+    fn list_prompts(&self) -> Vec<Prompt> {
+        vec![Prompt::new(
+            "example_prompt",
+            Some("This is an example prompt that takes one required agrument, message"),
+            Some(vec![PromptArgument {
+                name: "message".to_string(),
+                description: Some("A message to put in the prompt".to_string()),
+                required: Some(true),
+            }]),
+        )]
+    }
+
+    fn get_prompt(
+        &self,
+        prompt_name: &str,
+    ) -> Pin<Box<dyn Future<Output = Result<String, PromptError>> + Send + 'static>> {
+        let prompt_name = prompt_name.to_string();
+        Box::pin(async move {
+            match prompt_name.as_str() {
+                "example_prompt" => {
+                    let prompt = "This is an example prompt with your message here: '{message}'";
+                    Ok(prompt.to_string())
+                }
+                _ => Err(PromptError::NotFound(format!(
+                    "Prompt {} not found",
+                    prompt_name
+                ))),
+            }
+        })
+    }
 }
 
 #[tokio::main]

crates/mcp-server/src/router.rs

@@ -97,12 +97,8 @@ pub trait Router: Send + Sync + 'static {
         &self,
         uri: &str,
     ) -> Pin<Box<dyn Future<Output = Result<String, ResourceError>> + Send + 'static>>;
-    fn list_prompts(&self) -> Option<Vec<Prompt>> {
-        None
-    }
-    fn get_prompt(&self, _prompt_name: &str) -> Option<PromptFuture> {
-        None
-    }
+    fn list_prompts(&self) -> Vec<Prompt>;
+    fn get_prompt(&self, prompt_name: &str) -> PromptFuture;
 
     // Helper method to create base response
     fn create_response(&self, id: Option<u64>) -> JsonRpcResponse {
@@ -257,7 +253,7 @@ pub trait Router: Send + Sync + 'static {
         req: JsonRpcRequest,
     ) -> impl Future<Output = Result<JsonRpcResponse, RouterError>> + Send {
         async move {
-            let prompts = self.list_prompts().unwrap_or_default();
+            let prompts = self.list_prompts();
 
             let result = ListPromptsResult { prompts };
 
@@ -294,36 +290,36 @@ pub trait Router: Send + Sync + 'static {
                 .ok_or_else(|| RouterError::InvalidParams("Missing arguments object".into()))?;
 
             // Fetch the prompt definition first
-            let prompt = match self.list_prompts() {
-                Some(prompts) => prompts
-                    .into_iter()
-                    .find(|p| p.name == prompt_name)
-                    .ok_or_else(|| {
-                        RouterError::PromptNotFound(format!("Prompt '{}' not found", prompt_name))
-                    })?,
-                None => return Err(RouterError::PromptNotFound("No prompts available".into())),
-            };
+            let prompt = self
+                .list_prompts()
+                .into_iter()
+                .find(|p| p.name == prompt_name)
+                .ok_or_else(|| {
+                    RouterError::PromptNotFound(format!("Prompt '{}' not found", prompt_name))
+                })?;
 
             // 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
+                        )));
+                    }
                 }
             }
 
             // Now get the prompt content
             let description = self
                 .get_prompt(prompt_name)
-                .ok_or_else(|| RouterError::PromptNotFound("Prompt not found".into()))?
                 .await
                 .map_err(|e| RouterError::Internal(e.to_string()))?;