fix: catch tool registration errors

Author: cdcabrera

src/__tests__/__snapshots__/server.test.ts.snap

@@ -389,9 +389,6 @@ exports[`runServer should attempt to run server, register a tool: diagnostics 1`
     [
       "Built-in tool at index 0 is missing the static name property, "toolName"",
     ],
-    [
-      "Tool "loremIpsum" has a non Zod inputSchema. This may cause unexpected issues.",
-    ],
   ],
   "hasDebugLogs": true,
   "mcpServer": [
@@ -479,12 +476,6 @@ exports[`runServer should attempt to run server, register multiple tools: diagno
     [
       "Built-in tool at index 1 is missing the static name property, "toolName"",
     ],
-    [
-      "Tool "loremIpsum" has a non Zod inputSchema. This may cause unexpected issues.",
-    ],
-    [
-      "Tool "dolorSit" has a non Zod inputSchema. This may cause unexpected issues.",
-    ],
   ],
   "hasDebugLogs": true,
   "mcpServer": [

src/__tests__/options.context.test.ts

@@ -1,3 +1,4 @@
+import { z } from 'zod';
 import { McpServer } from '@modelcontextprotocol/sdk/server/mcp.js';
 import { StdioServerTransport } from '@modelcontextprotocol/sdk/server/stdio.js';
 import { runServer, type McpTool } from '../server';
@@ -122,7 +123,7 @@ describe('tool creator options context', () => {
 
       return [
         'alsContract',
-        { description: 'Context test tool', inputSchema: {} },
+        { description: 'Context test tool', inputSchema: z.object({}) },
         callback
       ];
     };

src/__tests__/server.test.ts

@@ -1,3 +1,4 @@
+import { z } from 'zod';
 import { McpServer } from '@modelcontextprotocol/sdk/server/mcp.js';
 import { StdioServerTransport } from '@modelcontextprotocol/sdk/server/stdio.js';
 import { runServer } from '../server';
@@ -112,7 +113,7 @@ describe('runServer', () => {
       tools: [
         jest.fn().mockReturnValue([
           'loremIpsum',
-          { description: 'Lorem Ipsum', inputSchema: {} },
+          { description: 'Lorem Ipsum', inputSchema: z.object({}) },
           jest.fn()
         ])
       ],
@@ -124,12 +125,12 @@ describe('runServer', () => {
       tools: [
         jest.fn().mockReturnValue([
           'loremIpsum',
-          { description: 'Lorem Ipsum', inputSchema: {} },
+          { description: 'Lorem Ipsum', inputSchema: z.object({}) },
           jest.fn()
         ]),
         jest.fn().mockReturnValue([
           'dolorSit',
-          { description: 'Dolor Sit', inputSchema: {} },
+          { description: 'Dolor Sit', inputSchema: z.object({}) },
           jest.fn()
         ])
       ],

src/server.ts

@@ -386,49 +386,55 @@ const runServer = async (options: ServerOptions = getOptions(), {
       const isZod = isZodSchema(schema?.inputSchema) || isZodRawShape(schema?.inputSchema);
       const isSchemaDefined = schema?.inputSchema !== undefined;
 
-      log.info(`Registered tool: ${name}`);
-
       if (!isZod) {
-        log.warn(`Tool "${name}" has a non Zod inputSchema. This may cause unexpected issues.`);
+        log.warn(`Tool "${name}" has a non Zod inputSchema. Skipping registration.`);
         log.debug(
           `Tool "${name}" has received a non Zod inputSchema from the tool pipeline.`,
           `This will cause unexpected issues, such as failure to pass arguments.`,
           `MCP SDK requires Zod. Kneel before Zod.`
         );
+
+        return;
       }
 
       // Lightweight check for malformed schemas that bypass validation.
       const isContextLike = (value: unknown) => isPlainObject(value) && 'requestId' in value && 'signal' in value;
 
-      server?.registerTool(name, schema, (args: unknown = {}, ..._args: unknown[]) =>
-        runWithSession(session, async () =>
-          runWithOptions(options, async () => {
-            // Basic track for remaining args to account for future MCP SDK alterations.
-            log.debug(
-              `Running tool "${name}"`,
-              `isArgs = ${args !== undefined}`,
-              `isRemainingArgs = ${_args?.length > 0}`
-            );
-
-            const timedReport = stat.traffic();
-            const isContextLikeArgs = isContextLike(args);
-
-            // Log potential Zod validation errors triggered by context fail.
-            if (isContextLikeArgs) {
+      try {
+        server?.registerTool(name, schema, (args: unknown = {}, ..._args: unknown[]) =>
+          runWithSession(session, async () =>
+            runWithOptions(options, async () => {
+              // Basic track for remaining args to account for future MCP SDK alterations.
               log.debug(
-                `Tool "${name}" handler received a context like object as the first parameter.`,
-                'If this is unexpected this is likely an undefined schema or a schema not registering as Zod.',
-                'Review the related schema definition and ensure it is defined and valid.',
-                `Schema is Defined = ${isSchemaDefined}; Schema is Zod = ${isZod}; Context like = ${isContextLikeArgs};`
+                `Running tool "${name}"`,
+                `isArgs = ${args !== undefined}`,
+                `isRemainingArgs = ${_args?.length > 0}`
               );
-            }
 
-            const toolResult = await callback(args);
+              const timedReport = stat.traffic();
+              const isContextLikeArgs = isContextLike(args);
+
+              // Log potential Zod validation errors triggered by context fail.
+              if (isContextLikeArgs) {
+                log.debug(
+                  `Tool "${name}" handler received a context like object as the first parameter.`,
+                  'If this is unexpected this is likely an undefined schema or a schema not registering as Zod.',
+                  'Review the related schema definition and ensure it is defined and valid.',
+                  `Schema is Defined = ${isSchemaDefined}; Schema is Zod = ${isZod}; Context like = ${isContextLikeArgs};`
+                );
+              }
+
+              const toolResult = await callback(args);
 
-            timedReport({ tool: name });
+              timedReport({ tool: name });
 
-            return toolResult;
-          })));
+              return toolResult;
+            })));
+
+        log.info(`Registered tool: ${name}`);
+      } catch (error) {
+        log.error(`Failed to register tool "${name}":`, error);
+      }
     });
 
     if (enableSigint && !sigintHandler) {