fix: pass tool schema without conversion (#56)

Author: benjamincburns

__tests__/tools.test.ts

@@ -1,6 +1,9 @@
 import { describe, test, expect, beforeEach, vi, MockedObject } from "vitest";
 import type { Client } from "@modelcontextprotocol/sdk/client/index.js";
-import type { StructuredTool } from "@langchain/core/tools";
+import {
+  StructuredTool,
+  ToolInputParsingException,
+} from "@langchain/core/tools";
 import type {
   EmbeddedResource,
   ImageContent,
@@ -59,6 +62,74 @@ describe("Simplified Tool Adapter Tests", () => {
       expect(tools[1].name).toBe("tool2");
     });
 
+    test("should validate tool input against input schema", async () => {
+      // Set up mock response
+      mockClient.listTools.mockReturnValueOnce(
+        Promise.resolve({
+          tools: [
+            {
+              name: "weather",
+              description: "Get the weather for a given city",
+              inputSchema: {
+                type: "object",
+                properties: {
+                  city: { type: "string" },
+                },
+                required: ["city"],
+              },
+            },
+          ],
+        })
+      );
+
+      mockClient.callTool.mockImplementation((params) => {
+        // should not be called if input is invalid
+        const args = params.arguments as { city: string };
+        expect(args.city).toBeDefined();
+        expect(typeof args.city).toBe("string");
+
+        return Promise.resolve({
+          content: [
+            {
+              type: "text",
+              text: `It is currently 70 degrees and cloudy in ${args.city}.`,
+            },
+          ],
+        });
+      });
+
+      // Load tools
+      const tools = await loadMcpTools(
+        "mockServer(should validate tool input against input schema)",
+        mockClient as Client
+      );
+
+      // Verify results
+      expect(tools.length).toBe(1);
+      expect(tools[0].name).toBe("weather");
+
+      const weatherTool = tools[0];
+
+      // should not invoke the tool when input is invalid
+      await expect(
+        weatherTool.invoke({ location: "New York" })
+      ).rejects.toThrow(ToolInputParsingException);
+
+      expect(mockClient.callTool).not.toHaveBeenCalled();
+
+      // should invoke the tool when input is valid
+      await expect(weatherTool.invoke({ city: "New York" })).resolves.toEqual(
+        "It is currently 70 degrees and cloudy in New York."
+      );
+
+      expect(mockClient.callTool).toHaveBeenCalledWith({
+        arguments: {
+          city: "New York",
+        },
+        name: "weather",
+      });
+    });
+
     test("should handle empty tool list", async () => {
       // Set up mock response
       mockClient.listTools.mockReturnValueOnce(

examples/langgraph_example.ts

@@ -10,7 +10,7 @@
  * - Built-in persistence capabilities
  *
  * In this example, we:
- * 1. Set up an MCP client to connect to the MCP Math server reference example
+ * 1. Set up an MCP client to connect to the MCP everything server reference example
  * 2. Create a LangGraph workflow with two nodes: one for the LLM and one for tools
  * 3. Define the edges and conditional routing between the nodes
  * 4. Execute the workflow with example queries
@@ -42,20 +42,20 @@ dotenv.config();
 
 /**
  * Example demonstrating how to use MCP tools with LangGraph agent flows
- * This example connects to a math server and uses its tools
+ * This example connects to a everything server and uses its tools
  */
 async function runExample() {
   let client: MultiServerMCPClient | null = null;
 
   try {
     console.log("Initializing MCP client...");
 
-    // Create a client with configurations for the math server only
+    // Create a client with configurations for the everything server only
     client = new MultiServerMCPClient({
-      math: {
+      everything: {
         transport: "stdio",
         command: "npx",
-        args: ["-y", "@modelcontextprotocol/server-math"],
+        args: ["-y", "@modelcontextprotocol/server-everything"],
       },
     });
 
@@ -137,7 +137,9 @@ async function runExample() {
     const app = workflow.compile();
 
     // Define queries for testing
-    const queries = ["What is 5 + 3?", "What is 7 * 9?"];
+    const queries = [
+      "If Sally has 420324 apples and mark steals 7824 of them, how many does she have left?",
+    ];
 
     // Test the LangGraph agent with the queries
     console.log("\n=== RUNNING LANGGRAPH AGENT ===");

package.json

@@ -52,16 +52,16 @@
     "zod": "^3.24.2"
   },
   "peerDependencies": {
-    "@langchain/core": "^0.3.40"
+    "@langchain/core": "^0.3.44"
   },
   "optionalDependencies": {
     "extended-eventsource": "^1.x"
   },
   "devDependencies": {
     "@eslint/js": "^9.21.0",
-    "@langchain/core": "^0.3.43",
+    "@langchain/core": "^0.3.44",
     "@langchain/langgraph": "^0.2.62",
-    "@langchain/openai": "^0.5.2",
+    "@langchain/openai": "^0.5.5",
     "@langchain/scripts": "^0.1.3",
     "@tsconfig/recommended": "^1.0.8",
     "@types/debug": "^4.1.12",
@@ -91,7 +91,8 @@
     "vitest": "^3.1.1"
   },
   "resolutions": {
-    "typescript": "4.9.5"
+    "typescript": "4.9.5",
+    "uuid": "^11.0.0"
   },
   "engines": {
     "node": ">=18"

src/tools.ts

@@ -18,19 +18,8 @@ import {
   MessageContentImageUrl,
   MessageContentText,
 } from "@langchain/core/messages";
-import type { JSONSchema } from "@dmitryrechkin/json-schema-to-zod";
-import type { ZodSchema } from "zod";
 import debug from "debug";
 
-let JSONSchemaToZod: { convert: (schema: JSONSchema) => ZodSchema } | undefined;
-
-async function convertSchema(schema: JSONSchema): Promise<ZodSchema> {
-  if (!JSONSchemaToZod) {
-    ({ JSONSchemaToZod } = await import("@dmitryrechkin/json-schema-to-zod"));
-  }
-  return JSONSchemaToZod.convert(schema);
-}
-
 // Replace direct initialization with lazy initialization
 let debugLog: debug.Debugger;
 function getDebugLog() {
@@ -279,12 +268,7 @@ export async function loadMcpTools(
             const dst = new DynamicStructuredTool({
               name: `${toolNamePrefix}${tool.name}`,
               description: tool.description || "",
-              schema: await convertSchema(
-                (tool.inputSchema ?? {
-                  type: "object",
-                  properties: {},
-                }) as JSONSchema
-              ),
+              schema: tool.inputSchema,
               responseFormat: "content_and_artifact",
               func: _callTool.bind(
                 null,

yarn.lock

@@ -438,9 +438,9 @@ __metadata:
   languageName: node
   linkType: hard
 
-"@langchain/core@npm:^0.3.43":
-  version: 0.3.43
-  resolution: "@langchain/core@npm:0.3.43"
+"@langchain/core@npm:^0.3.44":
+  version: 0.3.44
+  resolution: "@langchain/core@npm:0.3.44"
   dependencies:
     "@cfworker/json-schema": ^4.0.2
     ansi-styles: ^5.0.0
@@ -454,7 +454,7 @@ __metadata:
     uuid: ^10.0.0
     zod: ^3.22.4
     zod-to-json-schema: ^3.22.3
-  checksum: 5e5e9cd1ce39891177bc1d0d240785b60edeb0f9d53bb78a2ce394adf6fd15b972b63fb7a9d13c1f7b1341c79631baaa77225f6df36f509d0a606fb350f1d60f
+  checksum: d517305ec4fa0b0924b0224d3876eff621bbf97c673819910c53920d9c614db2c2293dc4b14ff408f517183b2aff9c7ea5a37eb2c4b8926b0c7605ca72b9f3cb
   languageName: node
   linkType: hard
 
@@ -513,9 +513,9 @@ __metadata:
   dependencies:
     "@dmitryrechkin/json-schema-to-zod": ^1.0.1
     "@eslint/js": ^9.21.0
-    "@langchain/core": ^0.3.43
+    "@langchain/core": ^0.3.44
     "@langchain/langgraph": ^0.2.62
-    "@langchain/openai": ^0.5.2
+    "@langchain/openai": ^0.5.5
     "@langchain/scripts": ^0.1.3
     "@modelcontextprotocol/sdk": ^1.7.0
     "@tsconfig/recommended": ^1.0.8
@@ -548,24 +548,24 @@ __metadata:
     vitest: ^3.1.1
     zod: ^3.24.2
   peerDependencies:
-    "@langchain/core": ^0.3.40
+    "@langchain/core": ^0.3.44
   dependenciesMeta:
     extended-eventsource:
       optional: true
   languageName: unknown
   linkType: soft
 
-"@langchain/openai@npm:^0.5.2":
-  version: 0.5.2
-  resolution: "@langchain/openai@npm:0.5.2"
+"@langchain/openai@npm:^0.5.5":
+  version: 0.5.5
+  resolution: "@langchain/openai@npm:0.5.5"
   dependencies:
     js-tiktoken: ^1.0.12
     openai: ^4.87.3
     zod: ^3.22.4
     zod-to-json-schema: ^3.22.3
   peerDependencies:
     "@langchain/core": ">=0.3.39 <0.4.0"
-  checksum: 34c941c0d086b2e575e781506765322aac3bc54af2f0086aa51ca759a46d2c8b2bc20b7e3f618f71e6d73d97815b65bc057bf982a9f6719d4a46059cc3244d3a
+  checksum: 45268375ee66f847a4b5ce64dbca86ad8ad07f0c6c6c9e23c50851f7abd501f841806aac7fb08c2213e6f2ef9f7ca3373243ff59e695626be22752114bfee142
   languageName: node
   linkType: hard
 
@@ -7730,21 +7730,12 @@ __metadata:
   languageName: node
   linkType: hard
 
-"uuid@npm:^10.0.0":
-  version: 10.0.0
-  resolution: "uuid@npm:10.0.0"
-  bin:
-    uuid: dist/bin/uuid
-  checksum: 4b81611ade2885d2313ddd8dc865d93d8dccc13ddf901745edca8f86d99bc46d7a330d678e7532e7ebf93ce616679fb19b2e3568873ac0c14c999032acb25869
-  languageName: node
-  linkType: hard
-
-"uuid@npm:^9.0.0":
-  version: 9.0.1
-  resolution: "uuid@npm:9.0.1"
+"uuid@npm:^11.0.0":
+  version: 11.1.0
+  resolution: "uuid@npm:11.1.0"
   bin:
-    uuid: dist/bin/uuid
-  checksum: 39931f6da74e307f51c0fb463dc2462807531dc80760a9bff1e35af4316131b4fc3203d16da60ae33f07fdca5b56f3f1dd662da0c99fea9aaeab2004780cc5f4
+    uuid: dist/esm/bin/uuid
+  checksum: 840f19758543c4631e58a29439e51b5b669d5f34b4dd2700b6a1d15c5708c7a6e0c3e2c8c4a2eae761a3a7caa7e9884d00c86c02622ba91137bd3deade6b4b4a
   languageName: node
   linkType: hard