feat: add createCollection tool (#76)

Author: nirinchev

src/tools/mongodb/create/createCollection.ts

@@ -0,0 +1,26 @@
+import { CallToolResult } from "@modelcontextprotocol/sdk/types.js";
+import { DbOperationArgs, MongoDBToolBase } from "../mongodbTool.js";
+import { OperationType, ToolArgs } from "../../tool.js";
+
+export class CreateCollectionTool extends MongoDBToolBase {
+    protected name = "create-collection";
+    protected description =
+        "Creates a new collection in a database. If the database doesn't exist, it will be created automatically.";
+    protected argsShape = DbOperationArgs;
+
+    protected operationType: OperationType = "create";
+
+    protected async execute({ collection, database }: ToolArgs<typeof this.argsShape>): Promise<CallToolResult> {
+        const provider = await this.ensureConnected();
+        await provider.createCollection(database, collection);
+
+        return {
+            content: [
+                {
+                    type: "text",
+                    text: `Collection "${collection}" created in database "${database}".`,
+                },
+            ],
+        };
+    }
+}

src/tools/mongodb/metadata/listCollections.ts

@@ -15,10 +15,21 @@ export class ListCollectionsTool extends MongoDBToolBase {
         const provider = await this.ensureConnected();
         const collections = await provider.listCollections(database);
 
+        if (collections.length === 0) {
+            return {
+                content: [
+                    {
+                        type: "text",
+                        text: `No collections found for database "${database}". To create a collection, use the "create-collection" tool.`,
+                    },
+                ],
+            };
+        }
+
         return {
             content: collections.map((collection) => {
                 return {
-                    text: `Name: ${collection.name}`,
+                    text: `Name: "${collection.name}"`,
                     type: "text",
                 };
             }),

src/tools/mongodb/tools.ts

@@ -19,6 +19,7 @@ import { RenameCollectionTool } from "./update/renameCollection.js";
 import { DropDatabaseTool } from "./delete/dropDatabase.js";
 import { DropCollectionTool } from "./delete/dropCollection.js";
 import { ExplainTool } from "./metadata/explain.js";
+import { CreateCollectionTool } from "./create/createCollection.js";
 
 export const MongoDbTools = [
     ConnectTool,
@@ -42,4 +43,5 @@ export const MongoDbTools = [
     DropDatabaseTool,
     DropCollectionTool,
     ExplainTool,
+    CreateCollectionTool,
 ];

tests/integration/helpers.ts

@@ -6,6 +6,16 @@ import path from "path";
 import fs from "fs/promises";
 import { Session } from "../../src/session.js";
 import { McpServer } from "@modelcontextprotocol/sdk/server/mcp.js";
+import { MongoClient } from "mongodb";
+import { toIncludeAllMembers } from "jest-extended";
+
+interface ParameterInfo {
+    name: string;
+    type: string;
+    description: string;
+}
+
+type ToolInfo = Awaited<ReturnType<Client["listTools"]>>["tools"][number];
 
 export function jestTestMCPClient(): () => Client {
     let client: Client | undefined;
@@ -59,8 +69,14 @@ export function jestTestMCPClient(): () => Client {
     };
 }
 
-export function jestTestCluster(): () => runner.MongoCluster {
+export function jestTestCluster(): () => { connectionString: string; getClient: () => MongoClient } {
     let cluster: runner.MongoCluster | undefined;
+    let client: MongoClient | undefined;
+
+    afterEach(async () => {
+        await client?.close();
+        client = undefined;
+    });
 
     beforeAll(async function () {
         // Downloading Windows executables in CI takes a long time because
@@ -108,7 +124,16 @@ export function jestTestCluster(): () => runner.MongoCluster {
             throw new Error("beforeAll() hook not ran yet");
         }
 
-        return cluster;
+        return {
+            connectionString: cluster.connectionString,
+            getClient: () => {
+                if (!client) {
+                    client = new MongoClient(cluster!.connectionString);
+                }
+
+                return client;
+            },
+        };
     };
 }
 
@@ -137,3 +162,30 @@ export async function connect(client: Client, cluster: runner.MongoCluster): Pro
         arguments: { connectionStringOrClusterName: cluster.connectionString },
     });
 }
+
+export function getParameters(tool: ToolInfo): ParameterInfo[] {
+    expect(tool.inputSchema.type).toBe("object");
+    expect(tool.inputSchema.properties).toBeDefined();
+
+    return Object.entries(tool.inputSchema.properties!)
+        .sort((a, b) => a[0].localeCompare(b[0]))
+        .map(([key, value]) => {
+            expect(value).toHaveProperty("type");
+            expect(value).toHaveProperty("description");
+
+            const typedValue = value as { type: string; description: string };
+            expect(typeof typedValue.type).toBe("string");
+            expect(typeof typedValue.description).toBe("string");
+            return {
+                name: key,
+                type: typedValue.type,
+                description: typedValue.description,
+            };
+        });
+}
+
+export function validateParameters(tool: ToolInfo, parameters: ParameterInfo[]): void {
+    const toolParameters = getParameters(tool);
+    expect(toolParameters).toHaveLength(parameters.length);
+    expect(toolParameters).toIncludeAllMembers(parameters);
+}

tests/integration/tools/mongodb/create/createCollection.test.ts

@@ -0,0 +1,129 @@
+import {
+    connect,
+    jestTestCluster,
+    jestTestMCPClient,
+    getResponseContent,
+    validateParameters,
+} from "../../../helpers.js";
+import { toIncludeSameMembers } from "jest-extended";
+import { McpError } from "@modelcontextprotocol/sdk/types.js";
+import { ObjectId } from "bson";
+
+describe("createCollection tool", () => {
+    const client = jestTestMCPClient();
+    const cluster = jestTestCluster();
+
+    it("should have correct metadata", async () => {
+        const { tools } = await client().listTools();
+        const listCollections = tools.find((tool) => tool.name === "create-collection")!;
+        expect(listCollections).toBeDefined();
+        expect(listCollections.description).toBe(
+            "Creates a new collection in a database. If the database doesn't exist, it will be created automatically."
+        );
+
+        validateParameters(listCollections, [
+            {
+                name: "database",
+                description: "Database name",
+                type: "string",
+            },
+            {
+                name: "collection",
+                description: "Collection name",
+                type: "string",
+            },
+        ]);
+    });
+
+    describe("with invalid arguments", () => {
+        const args = [
+            {},
+            { database: 123, collection: "bar" },
+            { foo: "bar", database: "test", collection: "bar" },
+            { collection: [], database: "test" },
+        ];
+        for (const arg of args) {
+            it(`throws a schema error for: ${JSON.stringify(arg)}`, async () => {
+                await connect(client(), cluster());
+                try {
+                    await client().callTool({ name: "create-collection", arguments: arg });
+                    expect.fail("Expected an error to be thrown");
+                } catch (error) {
+                    expect(error).toBeInstanceOf(McpError);
+                    const mcpError = error as McpError;
+                    expect(mcpError.code).toEqual(-32602);
+                    expect(mcpError.message).toContain("Invalid arguments for tool create-collection");
+                }
+            });
+        }
+    });
+
+    describe("with non-existent database", () => {
+        it("creates a new collection", async () => {
+            const mongoClient = cluster().getClient();
+            let collections = await mongoClient.db("foo").listCollections().toArray();
+            expect(collections).toHaveLength(0);
+
+            await connect(client(), cluster());
+            const response = await client().callTool({
+                name: "create-collection",
+                arguments: { database: "foo", collection: "bar" },
+            });
+            const content = getResponseContent(response.content);
+            expect(content).toEqual('Collection "bar" created in database "foo".');
+
+            collections = await mongoClient.db("foo").listCollections().toArray();
+            expect(collections).toHaveLength(1);
+            expect(collections[0].name).toEqual("bar");
+        });
+    });
+
+    describe("with existing database", () => {
+        let dbName: string;
+        beforeEach(() => {
+            dbName = new ObjectId().toString();
+        });
+
+        it("creates new collection", async () => {
+            const mongoClient = cluster().getClient();
+            await mongoClient.db(dbName).createCollection("collection1");
+            let collections = await mongoClient.db(dbName).listCollections().toArray();
+            expect(collections).toHaveLength(1);
+
+            await connect(client(), cluster());
+            const response = await client().callTool({
+                name: "create-collection",
+                arguments: { database: dbName, collection: "collection2" },
+            });
+            const content = getResponseContent(response.content);
+            expect(content).toEqual(`Collection "collection2" created in database "${dbName}".`);
+            collections = await mongoClient.db(dbName).listCollections().toArray();
+            expect(collections).toHaveLength(2);
+            expect(collections.map((c) => c.name)).toIncludeSameMembers(["collection1", "collection2"]);
+        });
+
+        it("does nothing if collection already exists", async () => {
+            const mongoClient = cluster().getClient();
+            await mongoClient.db(dbName).collection("collection1").insertOne({});
+            let collections = await mongoClient.db(dbName).listCollections().toArray();
+            expect(collections).toHaveLength(1);
+            let documents = await mongoClient.db(dbName).collection("collection1").find({}).toArray();
+            expect(documents).toHaveLength(1);
+
+            await connect(client(), cluster());
+            const response = await client().callTool({
+                name: "create-collection",
+                arguments: { database: dbName, collection: "collection1" },
+            });
+            const content = getResponseContent(response.content);
+            expect(content).toEqual(`Collection "collection1" created in database "${dbName}".`);
+            collections = await mongoClient.db(dbName).listCollections().toArray();
+            expect(collections).toHaveLength(1);
+            expect(collections[0].name).toEqual("collection1");
+
+            // Make sure we didn't drop the existing collection
+            documents = await mongoClient.db(dbName).collection("collection1").find({}).toArray();
+            expect(documents).toHaveLength(1);
+        });
+    });
+});

tests/integration/tools/mongodb/metadata/connect.test.ts

@@ -1,4 +1,4 @@
-import { getResponseContent, jestTestMCPClient, jestTestCluster } from "../../../helpers.js";
+import { getResponseContent, jestTestMCPClient, jestTestCluster, validateParameters } from "../../../helpers.js";
 
 import config from "../../../../../src/config.js";
 
@@ -11,20 +11,14 @@ describe("Connect tool", () => {
         const connectTool = tools.find((tool) => tool.name === "connect")!;
         expect(connectTool).toBeDefined();
         expect(connectTool.description).toBe("Connect to a MongoDB instance");
-        expect(connectTool.inputSchema.type).toBe("object");
-        expect(connectTool.inputSchema.properties).toBeDefined();
 
-        const propertyNames = Object.keys(connectTool.inputSchema.properties!);
-        expect(propertyNames).toHaveLength(1);
-        expect(propertyNames[0]).toBe("connectionStringOrClusterName");
-
-        const connectionStringOrClusterNameProp = connectTool.inputSchema.properties![propertyNames[0]] as {
-            type: string;
-            description: string;
-        };
-        expect(connectionStringOrClusterNameProp.type).toBe("string");
-        expect(connectionStringOrClusterNameProp.description).toContain("MongoDB connection string");
-        expect(connectionStringOrClusterNameProp.description).toContain("cluster name");
+        validateParameters(connectTool, [
+            {
+                name: "connectionStringOrClusterName",
+                description: "MongoDB connection string (in the mongodb:// or mongodb+srv:// format) or cluster name",
+                type: "string",
+            },
+        ]);
     });
 
     describe("with default config", () => {

tests/integration/tools/mongodb/metadata/listCollections.test.ts

@@ -0,0 +1,87 @@
+import {
+    getResponseElements,
+    connect,
+    jestTestCluster,
+    jestTestMCPClient,
+    getResponseContent,
+    getParameters,
+    validateParameters,
+} from "../../../helpers.js";
+import { toIncludeSameMembers } from "jest-extended";
+import { McpError } from "@modelcontextprotocol/sdk/types.js";
+
+describe("listCollections tool", () => {
+    const client = jestTestMCPClient();
+    const cluster = jestTestCluster();
+
+    it("should have correct metadata", async () => {
+        const { tools } = await client().listTools();
+        const listCollections = tools.find((tool) => tool.name === "list-collections")!;
+        expect(listCollections).toBeDefined();
+        expect(listCollections.description).toBe("List all collections for a given database");
+
+        validateParameters(listCollections, [{ name: "database", description: "Database name", type: "string" }]);
+    });
+
+    describe("with invalid arguments", () => {
+        const args = [{}, { database: 123 }, { foo: "bar", database: "test" }, { database: [] }];
+        for (const arg of args) {
+            it(`throws a schema error for: ${JSON.stringify(arg)}`, async () => {
+                await connect(client(), cluster());
+                try {
+                    await client().callTool({ name: "list-collections", arguments: arg });
+                    expect.fail("Expected an error to be thrown");
+                } catch (error) {
+                    expect(error).toBeInstanceOf(McpError);
+                    const mcpError = error as McpError;
+                    expect(mcpError.code).toEqual(-32602);
+                    expect(mcpError.message).toContain("Invalid arguments for tool list-collections");
+                    expect(mcpError.message).toContain('"expected": "string"');
+                }
+            });
+        }
+    });
+
+    describe("with non-existent database", () => {
+        it("returns no collections", async () => {
+            await connect(client(), cluster());
+            const response = await client().callTool({
+                name: "list-collections",
+                arguments: { database: "non-existent" },
+            });
+            const content = getResponseContent(response.content);
+            expect(content).toEqual(
+                `No collections found for database "non-existent". To create a collection, use the "create-collection" tool.`
+            );
+        });
+    });
+
+    describe("with existing database", () => {
+        it("returns collections", async () => {
+            const mongoClient = cluster().getClient();
+            await mongoClient.db("my-db").createCollection("collection-1");
+
+            await connect(client(), cluster());
+            const response = await client().callTool({
+                name: "list-collections",
+                arguments: { database: "my-db" },
+            });
+            const items = getResponseElements(response.content);
+            expect(items).toHaveLength(1);
+            expect(items[0].text).toContain('Name: "collection-1"');
+
+            await mongoClient.db("my-db").createCollection("collection-2");
+
+            const response2 = await client().callTool({
+                name: "list-collections",
+                arguments: { database: "my-db" },
+            });
+            const items2 = getResponseElements(response2.content);
+            expect(items2).toHaveLength(2);
+            expect(items2.map((item) => item.text)).toIncludeSameMembers([
+                'Name: "collection-1"',
+                'Name: "collection-2"',
+            ]);
+        });
+    });
+});