Merge pull request modelcontextprotocol#598 from connor4312/connor4312/597

fix: include previously-resolved variables in completions request

Author: dsp-ant

docs/specification/draft/server/utilities/completion.mdx

@@ -76,6 +76,49 @@ what is being completed through a reference type:
 }
 ```
 
+For prompts or URI templates with multiple arguments, clients should resolve them in the order they are presented by the server, and include each previous completion in the `context.arguments` object to provide context for subsequent requests.
+
+**Request:**
+
+```json
+{
+  "jsonrpc": "2.0",
+  "id": 1,
+  "method": "completion/complete",
+  "params": {
+    "ref": {
+      "type": "ref/prompt",
+      "name": "code_review"
+    },
+    "argument": {
+      "name": "framework",
+      "value": "fla"
+    },
+    "context": {
+      "arguments": {
+        "language": "python"
+      }
+    }
+  }
+}
+```
+
+**Response:**
+
+```json
+{
+  "jsonrpc": "2.0",
+  "id": 1,
+  "result": {
+    "completion": {
+      "values": ["flask"],
+      "total": 1,
+      "hasMore": false
+    }
+  }
+}
+```
+
 ### Reference Types
 
 The protocol supports two types of completion references:
@@ -117,6 +160,8 @@ sequenceDiagram
 - `argument`: Object containing:
   - `name`: Argument name
   - `value`: Current value
+- `context`: Object containing:
+  - `arguments`: A mapping of already-resolved argument names to their values.
 
 ### CompleteResult
 

schema/draft/schema.json

@@ -705,7 +705,7 @@ export interface CallToolResult extends Result {
    * Whether the tool call ended in an error.
    *
    * If not set, this is assumed to be false (the call was successful).
-   * 
+   *
    * Any errors that originate from the tool SHOULD be reported inside the result
    * object, with `isError` set to true, _not_ as an MCP protocol-level error
    * response. Otherwise, the LLM would not be able to see that an error occurred
@@ -816,7 +816,7 @@ export interface Tool {
   };
 
   /**
-   * An optional JSON Schema object defining the structure of the tool's output returned in 
+   * An optional JSON Schema object defining the structure of the tool's output returned in
    * the structuredContent field of a CallToolResult.
    */
   outputSchema?: {
@@ -1131,6 +1131,16 @@ export interface CompleteRequest extends Request {
        */
       value: string;
     };
+
+    /**
+     * Additional, optional context for completions
+     */
+    context?: {
+       /**
+        * Previously-resolved variables in a URI template or prompt.
+        */
+        arguments?: { [key: string]: string };
+     };
   };
 }
 
@@ -1258,7 +1268,7 @@ export interface ElicitRequest extends Request {
  * Restricted schema definitions that only allow primitive types
  * without nested objects or arrays.
  */
-export type PrimitiveSchemaDefinition = 
+export type PrimitiveSchemaDefinition =
   | StringSchema
   | NumberSchema
   | BooleanSchema
@@ -1307,7 +1317,7 @@ export interface ElicitResult extends Result {
    * - "cancel": User dismissed without making an explicit choice
    */
   action: "accept" | "decline" | "cancel";
-  
+
   /**
    * The submitted form data, only present when action is "accept".
    * Contains values matching the requested schema.