fix: don't use mcp error for our errors (#28)

Author: nirinchev

src/errors.ts

@@ -2,3 +2,12 @@ export enum ErrorCodes {
     NotConnectedToMongoDB = 1_000_000,
     InvalidParams = 1_000_001,
 }
+
+export class MongoDBError extends Error {
+    constructor(
+        public code: ErrorCodes,
+        message: string
+    ) {
+        super(message);
+    }
+}

src/tools/mongodb/connect.ts

@@ -1,9 +1,9 @@
 import { z } from "zod";
-import { CallToolResult, McpError } from "@modelcontextprotocol/sdk/types.js";
+import { CallToolResult } from "@modelcontextprotocol/sdk/types.js";
 import { NodeDriverServiceProvider } from "@mongosh/service-provider-node-driver";
 import { DbOperationType, MongoDBToolBase } from "./mongodbTool.js";
 import { ToolArgs } from "../tool";
-import { ErrorCodes } from "../../errors.js";
+import { ErrorCodes, MongoDBError } from "../../errors.js";
 
 export class ConnectTool extends MongoDBToolBase {
     protected name = "connect";
@@ -54,7 +54,7 @@ export class ConnectTool extends MongoDBToolBase {
                 };
             }
         } else {
-            throw new McpError(ErrorCodes.InvalidParams, "Invalid connection options");
+            throw new MongoDBError(ErrorCodes.InvalidParams, "Invalid connection options");
         }
 
         await this.connect(connectionString);

src/tools/mongodb/mongodbTool.ts

@@ -2,8 +2,8 @@ import { z } from "zod";
 import { ToolBase } from "../tool.js";
 import { State } from "../../state.js";
 import { NodeDriverServiceProvider } from "@mongosh/service-provider-node-driver";
-import { CallToolResult, McpError } from "@modelcontextprotocol/sdk/types.js";
-import { ErrorCodes } from "../../errors.js";
+import { CallToolResult } from "@modelcontextprotocol/sdk/types.js";
+import { ErrorCodes, MongoDBError } from "../../errors.js";
 
 export type MongoDBToolState = { serviceProvider?: NodeDriverServiceProvider };
 
@@ -27,14 +27,14 @@ export abstract class MongoDBToolBase extends ToolBase {
     protected ensureConnected(): NodeDriverServiceProvider {
         const provider = this.mongodbState.serviceProvider;
         if (!provider) {
-            throw new McpError(ErrorCodes.NotConnectedToMongoDB, "Not connected to MongoDB");
+            throw new MongoDBError(ErrorCodes.NotConnectedToMongoDB, "Not connected to MongoDB");
         }
 
         return provider;
     }
 
     protected handleError(error: unknown): CallToolResult | undefined {
-        if (error instanceof McpError && error.code === ErrorCodes.NotConnectedToMongoDB) {
+        if (error instanceof MongoDBError && error.code === ErrorCodes.NotConnectedToMongoDB) {
             return {
                 content: [
                     {