feat(meta): add _meta field to prompts, resources and paginated result (#558)

crates/rmcp/src/handler/server/router.rs

@@ -102,7 +102,7 @@ where
                 let tools = self.tool_router.list_all();
                 Ok(ServerResult::ListToolsResult(ListToolsResult {
                     tools,
-                    next_cursor: None,
+                    ..Default::default()
                 }))
             }
             ClientRequest::GetPromptRequest(request) => {
@@ -125,7 +125,7 @@ where
                 let prompts = self.prompt_router.list_all();
                 Ok(ServerResult::ListPromptsResult(ListPromptsResult {
                     prompts,
-                    next_cursor: None,
+                    ..Default::default()
                 }))
             }
             rest => self.service.handle_request(rest, context).await,

crates/rmcp/src/model.rs

@@ -828,6 +828,8 @@ macro_rules! paginated_result {
         #[serde(rename_all = "camelCase")]
         #[cfg_attr(feature = "schemars", derive(schemars::JsonSchema))]
         pub struct $t {
+            #[serde(rename = "_meta", skip_serializing_if = "Option::is_none")]
+            pub meta: Option<Meta>,
             #[serde(skip_serializing_if = "Option::is_none")]
             pub next_cursor: Option<Cursor>,
             pub $i_item: $t_item,
@@ -838,6 +840,7 @@ macro_rules! paginated_result {
                 items: $t_item,
             ) -> Self {
                 Self {
+                    meta: None,
                     next_cursor: None,
                     $i_item: items,
                 }

crates/rmcp/src/model/content.rs

@@ -258,6 +258,7 @@ mod tests {
             mime_type: Some("text/plain".to_string()),
             size: Some(100),
             icons: None,
+            meta: None,
         });
 
         let json = serde_json::to_string(&resource_link).unwrap();

crates/rmcp/src/model/prompt.rs

@@ -2,7 +2,7 @@ use base64::engine::{Engine, general_purpose::STANDARD as BASE64_STANDARD};
 use serde::{Deserialize, Serialize};
 
 use super::{
-    AnnotateAble, Annotations, Icon, RawEmbeddedResource, RawImageContent,
+    AnnotateAble, Annotations, Icon, Meta, RawEmbeddedResource, RawImageContent,
     content::{EmbeddedResource, ImageContent},
     resource::ResourceContents,
 };
@@ -25,6 +25,9 @@ pub struct Prompt {
     /// Optional list of icons for the prompt
     #[serde(skip_serializing_if = "Option::is_none")]
     pub icons: Option<Vec<Icon>>,
+    /// Optional additional metadata for this prompt
+    #[serde(rename = "_meta", skip_serializing_if = "Option::is_none")]
+    pub meta: Option<Meta>,
 }
 
 impl Prompt {
@@ -44,6 +47,7 @@ impl Prompt {
             description: description.map(Into::into),
             arguments,
             icons: None,
+            meta: None,
         }
     }
 }

crates/rmcp/src/model/resource.rs

@@ -29,6 +29,9 @@ pub struct RawResource {
     /// Optional list of icons for the resource
     #[serde(skip_serializing_if = "Option::is_none")]
     pub icons: Option<Vec<Icon>>,
+    /// Optional additional metadata for this resource
+    #[serde(rename = "_meta", skip_serializing_if = "Option::is_none")]
+    pub meta: Option<Meta>,
 }
 
 pub type Resource = Annotated<RawResource>;
@@ -95,6 +98,7 @@ impl RawResource {
             mime_type: None,
             size: None,
             icons: None,
+            meta: None,
         }
     }
 }
@@ -115,6 +119,7 @@ mod tests {
             mime_type: Some("text/plain".to_string()),
             size: Some(100),
             icons: None,
+            meta: None,
         };
 
         let json = serde_json::to_string(&resource).unwrap();