diff --git a/packages/client/src/client/client.ts b/packages/client/src/client/client.ts
index 9c2c87290..b0a8e1c83 100644
--- a/packages/client/src/client/client.ts
+++ b/packages/client/src/client/client.ts
@@ -24,11 +24,11 @@ import type {
     ReadResourceRequest,
     Request,
     RequestHandlerExtra,
-    RequestMethod,
     RequestOptions,
     RequestTypeMap,
     Result,
     ServerCapabilities,
+    ServerToClientRequestMethod,
     SubscribeRequest,
     Tool,
     Transport,
@@ -327,8 +327,10 @@ export class Client<
 
     /**
      * Override request handler registration to enforce client-side validation for elicitation.
+     * Only server-to-client methods are valid (sampling/createMessage, elicitation/create, roots/list).
      */
-    public override setRequestHandler<M extends RequestMethod>(
+    // @ts-expect-error - Intentionally narrowing the method constraint for type safety
+    public override setRequestHandler<M extends ServerToClientRequestMethod>(
         method: M,
         handler: (
             request: RequestTypeMap[M],
diff --git a/packages/core/src/types/types.ts b/packages/core/src/types/types.ts
index 9d659693f..63b0222f5 100644
--- a/packages/core/src/types/types.ts
+++ b/packages/core/src/types/types.ts
@@ -2615,6 +2615,10 @@ export type NotificationMethod = ClientNotification['method'] | ServerNotificati
 export type RequestTypeMap = MethodToTypeMap<ClientRequest | ServerRequest>;
 export type NotificationTypeMap = MethodToTypeMap<ClientNotification | ServerNotification>;
 
+// Narrowed method types for Client and Server request handlers
+export type ServerToClientRequestMethod = ServerRequest['method'];
+export type ClientToServerRequestMethod = ClientRequest['method'];
+
 /* Runtime schema lookup */
 type RequestSchemaType = (typeof ClientRequestSchema.options)[number] | (typeof ServerRequestSchema.options)[number];
 type NotificationSchemaType = (typeof ClientNotificationSchema.options)[number] | (typeof ServerNotificationSchema.options)[number];
diff --git a/packages/server/src/server/server.ts b/packages/server/src/server/server.ts
index ca43272cf..7c9bd9c8d 100644
--- a/packages/server/src/server/server.ts
+++ b/packages/server/src/server/server.ts
@@ -1,5 +1,6 @@
 import type {
     ClientCapabilities,
+    ClientToServerRequestMethod,
     CreateMessageRequest,
     CreateMessageRequestParamsBase,
     CreateMessageRequestParamsWithTools,
@@ -21,7 +22,6 @@ import type {
     ProtocolOptions,
     Request,
     RequestHandlerExtra,
-    RequestMethod,
     RequestOptions,
     RequestTypeMap,
     ResourceUpdatedNotification,
@@ -214,8 +214,10 @@ export class Server<
 
     /**
      * Override request handler registration to enforce server-side validation for tools/call.
+     * Only client-to-server methods are valid (tools/call, prompts/get, resources/read, etc.).
      */
-    public override setRequestHandler<M extends RequestMethod>(
+    // @ts-expect-error - Intentionally narrowing the method constraint for type safety
+    public override setRequestHandler<M extends ClientToServerRequestMethod>(
         method: M,
         handler: (
             request: RequestTypeMap[M],