Allow prompts to embed resources

Author: jspahrsummers

schema/schema.json

@@ -418,7 +418,7 @@
                 },
                 "messages": {
                     "items": {
-                        "$ref": "#/definitions/SamplingMessage"
+                        "$ref": "#/definitions/PromptMessage"
                     },
                     "type": "array"
                 }
@@ -1166,6 +1166,36 @@
             ],
             "type": "object"
         },
+        "PromptMessage": {
+            "description": "Describes a message returned as part of a prompt.\n\nThis is similar to `SamplingMessage`, but also supports the embedding of\nresource contents from the MCP server. The client MUST decide how to render\nembedded resources for the benefit of the LLM and/or the user.",
+            "properties": {
+                "content": {
+                    "anyOf": [
+                        {
+                            "$ref": "#/definitions/ResourceContents"
+                        },
+                        {
+                            "$ref": "#/definitions/TextContent"
+                        },
+                        {
+                            "$ref": "#/definitions/ImageContent"
+                        }
+                    ]
+                },
+                "role": {
+                    "enum": [
+                        "assistant",
+                        "user"
+                    ],
+                    "type": "string"
+                }
+            },
+            "required": [
+                "content",
+                "role"
+            ],
+            "type": "object"
+        },
         "PromptReference": {
             "description": "Identifies a prompt.",
             "properties": {

schema/schema.ts

@@ -157,10 +157,6 @@ export interface ClientCapabilities {
    * Experimental, non-standard capabilities that the client supports.
    */
   experimental?: { [key: string]: object };
-  /**
-   * Present if the client supports sampling from an LLM.
-   */
-  sampling?: object;
   /**
    * Present if the client supports listing roots.
    */
@@ -170,6 +166,10 @@ export interface ClientCapabilities {
      */
     listChanged?: boolean;
   };
+  /**
+   * Present if the client supports sampling from an LLM.
+   */
+  sampling?: object;
 }
 
 /**
@@ -515,7 +515,7 @@ export interface GetPromptResult extends Result {
    * An optional description for the prompt.
    */
   description?: string;
-  messages: SamplingMessage[];
+  messages: PromptMessage[];
 }
 
 /**
@@ -554,6 +554,18 @@ export interface PromptArgument {
   required?: boolean;
 }
 
+/**
+ * Describes a message returned as part of a prompt.
+ *
+ * This is similar to `SamplingMessage`, but also supports the embedding of
+ * resource contents from the MCP server. The client MUST decide how to render
+ * embedded resources for the benefit of the LLM and/or the user.
+ */
+export interface PromptMessage {
+  role: "user" | "assistant";
+  content: TextContent | ImageContent | ResourceContents;
+}
+
 /**
  * An optional notification from the server to the client, informing it that the list of prompts it offers has changed. This may be issued by servers without any previous subscription from the client.
  */