[RFC] refactor: remove vestigial generic type parameters from Protocol, Server, and Client (modelcontextprotocol#1451)

Author: felixweinberger

examples/client/src/simpleStreamableHttp.ts

@@ -293,7 +293,7 @@ async function connect(url?: string): Promise<void> {
                 attempts++;
                 console.log(`\nPlease provide the following information (attempt ${attempts}/${maxAttempts}):`);
 
-                const content: Record<string, unknown> = {};
+                const content: Record<string, string | number | boolean | string[]> = {};
                 let inputCancelled = false;
 
                 // Collect input for each field
@@ -357,7 +357,7 @@ async function connect(url?: string): Promise<void> {
                     // Parse and validate the input
                     try {
                         if (answer === '' && field.default !== undefined) {
-                            content[fieldName] = field.default;
+                            content[fieldName] = field.default as string | number | boolean | string[];
                         } else if (answer === '' && !isRequired) {
                             // Skip optional empty fields
                             continue;
@@ -401,7 +401,7 @@ async function connect(url?: string): Promise<void> {
                                 }
                             }
 
-                            content[fieldName] = parsedValue;
+                            content[fieldName] = parsedValue as string | number | boolean | string[];
                         }
                     } catch (error) {
                         console.log(`❌ Error: ${error}`);

packages/client/src/client/client.ts

@@ -22,15 +22,13 @@ import type {
     ListToolsRequest,
     LoggingLevel,
     MessageExtraInfo,
-    Notification,
     NotificationMethod,
     ProtocolOptions,
     ReadResourceRequest,
-    Request,
     RequestMethod,
     RequestOptions,
     RequestTypeMap,
-    Result,
+    ResultTypeMap,
     ServerCapabilities,
     SubscribeRequest,
     Tool,
@@ -193,36 +191,8 @@ export type ClientOptions = ProtocolOptions & {
  *
  * The client will automatically begin the initialization flow with the server when connect() is called.
  *
- * To use with custom types, extend the base Request/Notification/Result types and pass them as type parameters:
- *
- * ```typescript
- * // Custom schemas
- * const CustomRequestSchema = RequestSchema.extend({...})
- * const CustomNotificationSchema = NotificationSchema.extend({...})
- * const CustomResultSchema = ResultSchema.extend({...})
- *
- * // Type aliases
- * type CustomRequest = z.infer<typeof CustomRequestSchema>
- * type CustomNotification = z.infer<typeof CustomNotificationSchema>
- * type CustomResult = z.infer<typeof CustomResultSchema>
- *
- * // Create typed client
- * const client = new Client<CustomRequest, CustomNotification, CustomResult>({
- *   name: "CustomClient",
- *   version: "1.0.0"
- * })
- * ```
  */
-export class Client<
-    RequestT extends Request = Request,
-    NotificationT extends Notification = Notification,
-    ResultT extends Result = Result
-> extends Protocol<
-    ClientRequest | RequestT,
-    ClientNotification | NotificationT,
-    ClientResult | ResultT,
-    ClientContext<ClientRequest | RequestT, ClientNotification | NotificationT>
-> {
+export class Client extends Protocol<ClientContext> {
     private _serverCapabilities?: ServerCapabilities;
     private _serverVersion?: Implementation;
     private _capabilities: ClientCapabilities;
@@ -231,7 +201,7 @@ export class Client<
     private _cachedToolOutputValidators: Map<string, JsonSchemaValidator<unknown>> = new Map();
     private _cachedKnownTaskTools: Set<string> = new Set();
     private _cachedRequiredTaskTools: Set<string> = new Set();
-    private _experimental?: { tasks: ExperimentalClientTasks<RequestT, NotificationT, ResultT> };
+    private _experimental?: { tasks: ExperimentalClientTasks };
     private _listChangedDebounceTimers: Map<string, ReturnType<typeof setTimeout>> = new Map();
     private _pendingListChangedConfig?: ListChangedHandlers;
     private _enforceStrictCapabilities: boolean;
@@ -254,10 +224,7 @@ export class Client<
         }
     }
 
-    protected override buildContext(
-        ctx: BaseContext<ClientRequest | RequestT, ClientNotification | NotificationT>,
-        _transportInfo?: MessageExtraInfo
-    ): ClientContext<ClientRequest | RequestT, ClientNotification | NotificationT> {
+    protected override buildContext(ctx: BaseContext, _transportInfo?: MessageExtraInfo): ClientContext {
         return ctx;
     }
 
@@ -297,7 +264,7 @@ export class Client<
      *
      * @experimental
      */
-    get experimental(): { tasks: ExperimentalClientTasks<RequestT, NotificationT, ResultT> } {
+    get experimental(): { tasks: ExperimentalClientTasks } {
         if (!this._experimental) {
             this._experimental = {
                 tasks: new ExperimentalClientTasks(this)
@@ -324,16 +291,10 @@ export class Client<
      */
     public override setRequestHandler<M extends RequestMethod>(
         method: M,
-        handler: (
-            request: RequestTypeMap[M],
-            ctx: ClientContext<ClientRequest | RequestT, ClientNotification | NotificationT>
-        ) => ClientResult | ResultT | Promise<ClientResult | ResultT>
+        handler: (request: RequestTypeMap[M], ctx: ClientContext) => ResultTypeMap[M] | Promise<ResultTypeMap[M]>
     ): void {
         if (method === 'elicitation/create') {
-            const wrappedHandler = async (
-                request: RequestTypeMap[M],
-                ctx: ClientContext<ClientRequest | RequestT, ClientNotification | NotificationT>
-            ): Promise<ClientResult | ResultT> => {
+            const wrappedHandler = async (request: RequestTypeMap[M], ctx: ClientContext): Promise<ClientResult> => {
                 const validatedRequest = parseSchema(ElicitRequestSchema, request);
                 if (!validatedRequest.success) {
                     // Type guard: if success is false, error is guaranteed to exist
@@ -403,10 +364,7 @@ export class Client<
         }
 
         if (method === 'sampling/createMessage') {
-            const wrappedHandler = async (
-                request: RequestTypeMap[M],
-                ctx: ClientContext<ClientRequest | RequestT, ClientNotification | NotificationT>
-            ): Promise<ClientResult | ResultT> => {
+            const wrappedHandler = async (request: RequestTypeMap[M], ctx: ClientContext): Promise<ClientResult> => {
                 const validatedRequest = parseSchema(CreateMessageRequestSchema, request);
                 if (!validatedRequest.success) {
                     const errorMessage =
@@ -533,7 +491,7 @@ export class Client<
         return this._instructions;
     }
 
-    protected assertCapabilityForMethod(method: RequestT['method']): void {
+    protected assertCapabilityForMethod(method: RequestMethod): void {
         switch (method as ClientRequest['method']) {
             case 'logging/setLevel': {
                 if (!this._serverCapabilities?.logging) {
@@ -596,7 +554,7 @@ export class Client<
         }
     }
 
-    protected assertNotificationCapability(method: NotificationT['method']): void {
+    protected assertNotificationCapability(method: NotificationMethod): void {
         switch (method as ClientNotification['method']) {
             case 'notifications/roots/list_changed': {
                 if (!this._capabilities.roots?.listChanged) {

packages/client/src/experimental/tasks/client.ts

@@ -9,14 +9,11 @@ import type {
     AnyObjectSchema,
     CallToolRequest,
     CancelTaskResult,
-    ClientRequest,
     GetTaskResult,
     ListTasksResult,
-    Notification,
     Request,
     RequestOptions,
     ResponseMessage,
-    Result,
     SchemaOutput
 } from '@modelcontextprotocol/core';
 import { CallToolResultSchema, ProtocolError, ProtocolErrorCode } from '@modelcontextprotocol/core';
@@ -27,9 +24,9 @@ import type { Client } from '../../client/client.js';
  * Internal interface for accessing Client's private methods.
  * @internal
  */
-interface ClientInternal<RequestT extends Request> {
+interface ClientInternal {
     requestStream<T extends AnyObjectSchema>(
-        request: ClientRequest | RequestT,
+        request: Request,
         resultSchema: T,
         options?: RequestOptions
     ): AsyncGenerator<ResponseMessage<SchemaOutput<T>>, void, void>;
@@ -48,12 +45,8 @@ interface ClientInternal<RequestT extends Request> {
  *
  * @experimental
  */
-export class ExperimentalClientTasks<
-    RequestT extends Request = Request,
-    NotificationT extends Notification = Notification,
-    ResultT extends Result = Result
-> {
-    constructor(private readonly _client: Client<RequestT, NotificationT, ResultT>) {}
+export class ExperimentalClientTasks {
+    constructor(private readonly _client: Client) {}
 
     /**
      * Calls a tool and returns an AsyncGenerator that yields response messages.
@@ -96,7 +89,7 @@ export class ExperimentalClientTasks<
         options?: RequestOptions
     ): AsyncGenerator<ResponseMessage<SchemaOutput<typeof CallToolResultSchema>>, void, void> {
         // Access Client's internal methods
-        const clientInternal = this._client as unknown as ClientInternal<RequestT>;
+        const clientInternal = this._client as unknown as ClientInternal;
 
         // Add task creation parameters if server supports it and not explicitly provided
         const optionsWithTask = {
@@ -255,14 +248,14 @@ export class ExperimentalClientTasks<
      * @experimental
      */
     requestStream<T extends AnyObjectSchema>(
-        request: ClientRequest | RequestT,
+        request: Request,
         resultSchema: T,
         options?: RequestOptions
     ): AsyncGenerator<ResponseMessage<SchemaOutput<T>>, void, void> {
         // Delegate to the client's underlying Protocol method
         type ClientWithRequestStream = {
             requestStream<U extends AnyObjectSchema>(
-                request: ClientRequest | RequestT,
+                request: Request,
                 resultSchema: U,
                 options?: RequestOptions
             ): AsyncGenerator<ResponseMessage<SchemaOutput<U>>, void, void>;