fix: use dynamic database lookup for search index check

api-extractor/reports/mongodb-mcp-server.public.api.md

@@ -358,7 +358,7 @@ export class ConnectionStateConnected implements ConnectionState {
     // (undocumented)
     connectionStringInfo?: ConnectionStringInfo | undefined;
     // (undocumented)
-    isSearchSupported(): Promise<boolean>;
+    isSearchSupported(logger: LoggerBase): Promise<boolean>;
     // (undocumented)
     serviceProvider: NodeDriverServiceProvider;
     // (undocumented)

api-extractor/reports/web.public.api.md

@@ -382,7 +382,7 @@ export class ConnectionStateConnected implements ConnectionState {
     // (undocumented)
     connectionStringInfo?: ConnectionStringInfo | undefined;
     // (undocumented)
-    isSearchSupported(): Promise<boolean>;
+    isSearchSupported(logger: LoggerBase): Promise<boolean>;
     // (undocumented)
     serviceProvider: NodeDriverServiceProvider;
     // (undocumented)

package.json

@@ -137,7 +137,6 @@
     "husky": "^9.1.7",
     "jsdom": "^29.0.2",
     "knip": "^6.4.1",
-    "mongodb": "^7.1.1",
     "mongodb-runner": "^6.7.6",
     "openapi-types": "^12.1.3",
     "openapi-typescript": "^7.13.0",
@@ -173,6 +172,7 @@
     "express": "^5.2.1",
     "jsonc-parser": "^3.3.1",
     "lru-cache": "^11.2.6",
+    "mongodb": "^7.1.1",
     "mongodb-build-info": "^1.9.7",
     "mongodb-connection-string-url": "^7.0.1",
     "mongodb-log-writer": "^2.5.7",

src/common/connectionManager.ts

@@ -1,4 +1,5 @@
 import { EventEmitter } from "events";
+import { MongoServerError } from "mongodb";
 import { NodeDriverServiceProvider } from "@mongosh/service-provider-node-driver";
 import { generateConnectionInfoFromCliArgs, type ConnectionInfo } from "@mongosh/arg-parser";
 import type { DeviceId } from "../helpers/deviceId.js";
@@ -29,7 +30,10 @@ export interface ConnectionState {
     connectedAtlasCluster?: AtlasClusterConnectionInfo;
 }
 
-const MCP_TEST_DATABASE = "#mongodb-mcp";
+const SEARCH_PROBE_COLLECTION_NAME = "test";
+
+/** See https://github.com/mongodb/mongo/blob/master/src/mongo/base/error_codes.yml (SearchNotEnabled). */
+const MONGODB_SEARCH_NOT_ENABLED_ERROR_CODE = 31082;
 
 export const defaultDriverOptions: ConnectionInfo["driverOptions"] = {
     readConcern: {
@@ -55,21 +59,104 @@ export class ConnectionStateConnected implements ConnectionState {
 
     private _isSearchSupported?: boolean;
 
-    public async isSearchSupported(): Promise<boolean> {
+    public async isSearchSupported(logger: LoggerBase): Promise<boolean> {
         if (this._isSearchSupported === undefined) {
+            this._isSearchSupported = await this.probeSearchCapability(logger);
+        }
+
+        return this._isSearchSupported;
+    }
+
+    private async probeSearchCapability(logger: LoggerBase): Promise<boolean> {
+        const databases = await this.buildSearchProbeDatabaseCandidates(logger);
+
+        for (const databaseName of databases) {
             try {
-                // If a cluster supports search indexes, the call below will succeed
-                // with a cursor otherwise will throw an Error.
-                // the Search Index Management Service might not be ready yet, but
-                // we assume that the agent can retry in that situation.
-                await this.serviceProvider.getSearchIndexes(MCP_TEST_DATABASE, "test");
-                this._isSearchSupported = true;
-            } catch {
-                this._isSearchSupported = false;
+                await this.serviceProvider.getSearchIndexes(databaseName, SEARCH_PROBE_COLLECTION_NAME);
+                logger.debug({
+                    id: LogId.searchCapabilityProbe,
+                    context: "ConnectionStateConnected",
+                    message: "Atlas Search capability probe succeeded",
+                });
+                return true;
+            } catch (probeError: unknown) {
+                if (
+                    probeError instanceof MongoServerError &&
+                    (probeError.code === MONGODB_SEARCH_NOT_ENABLED_ERROR_CODE ||
+                        probeError.codeName === "SearchNotEnabled")
+                ) {
+                    logger.debug({
+                        id: LogId.searchCapabilityProbe,
+                        context: "ConnectionStateConnected",
+                        message: "Atlas Search capability probe: search not enabled on cluster",
+                    });
+
+                    return false;
+                }
+
+                logger.debug({
+                    id: LogId.searchCapabilityProbe,
+                    context: "ConnectionStateConnected",
+                    message: "Atlas Search capability probe: inconclusive error for database candidate, trying next",
+                });
             }
         }
 
-        return this._isSearchSupported;
+        logger.debug({
+            id: LogId.searchCapabilityProbe,
+            context: "ConnectionStateConnected",
+            message: "Atlas Search capability probe: no success and no SearchNotEnabled; assuming search is supported",
+        });
+
+        return true;
+    }
+
+    /**
+     * Build an ordered list of database names to try for the search index probe.
+     * Prefers the driver's initial database from the connection string (when not
+     * a system DB), then other non-system databases from listDatabases, then the
+     * fallback #mongodb-mcp database.
+     */
+    private async buildSearchProbeDatabaseCandidates(logger: LoggerBase): Promise<string[]> {
+        type ListDatabasesDocument = { databases?: { name?: string }[] };
+        let listedNames: string[] = [];
+        try {
+            const raw = (await this.serviceProvider.listDatabases("")) as ListDatabasesDocument;
+            const rows = raw.databases;
+            if (Array.isArray(rows)) {
+                listedNames = rows
+                    .map((row) => row.name)
+                    .filter((name): name is string => typeof name === "string" && name.length > 0);
+            }
+        } catch {
+            logger.debug({
+                id: LogId.searchCapabilityProbe,
+                context: "ConnectionStateConnected",
+                message: "listDatabases failed while building Atlas Search probe candidates",
+            });
+        }
+
+        // System databases that should be skipped when searching for accessible databases
+        const SYSTEM_DATABASES = new Set(["admin", "local", "config"]);
+
+        const nonSystem = listedNames
+            .filter((name) => !SYSTEM_DATABASES.has(name))
+            .slice(0, 10)
+            .sort((a, b) => a.localeCompare(b));
+
+        const result = new Set<string>();
+        const initialDb = this.serviceProvider.initialDb;
+        if (initialDb.length > 0 && !SYSTEM_DATABASES.has(initialDb)) {
+            result.add(initialDb);
+        }
+
+        for (const name of nonSystem) {
+            result.add(name);
+        }
+
+        result.add("#mongodb-mcp");
+
+        return [...result];
     }
 }
 

src/common/logging/loggingDefinitions.ts

@@ -40,6 +40,7 @@ export const LogId = {
     mongodbConnectTry: mongoLogId(1_004_003),
     mongodbCursorCloseError: mongoLogId(1_004_004),
     mongodbIndexCheckFailure: mongoLogId(1_004_005),
+    searchCapabilityProbe: mongoLogId(1_004_006),
 
     toolUpdateFailure: mongoLogId(1_005_001),
     resourceUpdateFailure: mongoLogId(1_005_002),

src/common/session.ts

@@ -156,7 +156,7 @@ export class Session extends EventEmitter<SessionEvents> {
     async isSearchSupported(): Promise<boolean> {
         const state = this.connectionManager.currentConnectionState;
         if (state.tag === "connected") {
-            return await state.isSearchSupported();
+            return await state.isSearchSupported(this.logger);
         }
 
         return false;