feat: allow to set server logging level

src/FastMCP.test.ts

@@ -16,7 +16,7 @@ const runWithTestServer = async ({
   start,
 }: {
   start: () => Promise<FastMCP>;
-  run: ({ client }: { client: Client }) => Promise<void>;
+  run: ({ client, server }: { client: Client, server: FastMCP }) => Promise<void>;
 }) => {
   const port = await getRandomPort();
 
@@ -47,7 +47,7 @@ const runWithTestServer = async ({
 
     await client.connect(transport);
 
-    await run({ client });
+    await run({ client, server });
   } finally {
     await server.stop();
   }
@@ -261,6 +261,32 @@ test("tracks tool progress", async () => {
   });
 });
 
+test("sets logging levels", async () => {
+  await runWithTestServer({
+    start: async () => {
+      const server = new FastMCP({
+        name: "Test",
+        version: "1.0.0",
+      });
+
+      return server;
+    },
+    run: async ({ client, server }) => {
+      await client.setLoggingLevel("debug");
+
+      expect(
+        server.loggingLevel,
+      ).toBe("debug");
+
+      await client.setLoggingLevel("info");
+
+      expect(
+        server.loggingLevel,
+      ).toBe("info");
+    },
+  });
+});
+
 test("adds resources", async () => {
   await runWithTestServer({
     start: async () => {

src/FastMCP.ts

@@ -11,6 +11,7 @@ import {
   McpError,
   ReadResourceRequestSchema,
   ServerCapabilities,
+  SetLevelRequestSchema,
 } from "@modelcontextprotocol/sdk/types.js";
 import { zodToJsonSchema } from "zod-to-json-schema";
 import type { z } from "zod";
@@ -107,6 +108,7 @@ export class FastMCP {
   #prompts: Prompt[];
   #server: Server | null = null;
   #options: ServerOptions;
+  #loggingLevel: LoggingLevel = "info";
 
   constructor(public options: ServerOptions) {
     this.#options = options;
@@ -129,6 +131,12 @@ export class FastMCP {
     if (this.#prompts.length) {
       this.setupPromptHandlers(server);
     }
+
+    server.setRequestHandler(SetLevelRequestSchema, (request) => {
+      this.#loggingLevel = request.params.level;
+
+      return {};
+    });
   }
 
   private setupErrorHandling(server: Server) {
@@ -141,6 +149,10 @@ export class FastMCP {
     });
   }
 
+  public get loggingLevel() {
+    return this.#loggingLevel;
+  }
+
   private setupToolHandlers(server: Server) {
     server.setRequestHandler(ListToolsRequestSchema, async () => {
       return {
@@ -380,6 +392,8 @@ export class FastMCP {
       capabilities.prompts = {};
     }
 
+    capabilities.logging = {};
+
     this.#server = new Server(
       { name: this.#options.name, version: this.#options.version },
       { capabilities },