Expose a basic version of the MCP server as an option for the dev CLI command

This just adds the main components for the MCP server. It hooks on the
existing `dev` command and can be enabled by passing the `--mcp` flag.

Currently only the `trigger-task` tool is exposed, which enables users
trigger tasks via MCP and see the resulting run.

Still WIP :)

Author: myftija

packages/cli-v3/package.json

@@ -49,6 +49,7 @@
     "@types/eventsource": "^1.1.15",
     "@types/gradient-string": "^1.1.2",
     "@types/object-hash": "3.0.6",
+    "@types/polka": "^0.5.7",
     "@types/react": "^18.2.48",
     "@types/resolve": "^1.20.6",
     "@types/rimraf": "^4.0.5",
@@ -75,6 +76,7 @@
   "dependencies": {
     "@clack/prompts": "^0.10.0",
     "@depot/cli": "0.0.1-cli.2.80.0",
+    "@modelcontextprotocol/sdk": "^1.6.1",
     "@opentelemetry/api": "1.9.0",
     "@opentelemetry/api-logs": "0.52.1",
     "@opentelemetry/exporter-logs-otlp-http": "0.52.1",
@@ -114,6 +116,7 @@
     "p-retry": "^6.1.0",
     "partysocket": "^1.0.2",
     "pkg-types": "^1.1.3",
+    "polka": "^0.5.2",
     "resolve": "^1.22.8",
     "semver": "^7.5.0",
     "signal-exit": "^4.1.0",

packages/cli-v3/src/apiClient.ts

@@ -31,6 +31,7 @@ import {
   DevDequeueRequestBody,
   DevDequeueResponseBody,
   PromoteDeploymentResponseBody,
+  ListRunResponse,
 } from "@trigger.dev/core/v3";
 import { zodfetch, zodfetchSSE, ApiError } from "@trigger.dev/core/v3/zodfetch";
 import { logger } from "./utilities/logger.js";
@@ -48,6 +49,7 @@ import {
 export class CliApiClient {
   constructor(
     public readonly apiURL: string,
+    // TODO: consider making this required
     public readonly accessToken?: string
   ) {
     this.apiURL = apiURL.replace(/\/$/, "");

packages/cli-v3/src/commands/dev.ts

@@ -20,6 +20,7 @@ const DevCommandOptions = CommonCommandOptions.extend({
   envFile: z.string().optional(),
   keepTmpFiles: z.boolean().default(false),
   maxConcurrentRuns: z.coerce.number().optional(),
+  mcp: z.boolean().default(false),
 });
 
 export type DevCommandOptions = z.infer<typeof DevCommandOptions>;
@@ -48,6 +49,8 @@ export function configureDevCommand(program: Command) {
         "--keep-tmp-files",
         "Keep temporary files after the dev session ends, helpful for debugging"
       )
+      // TODO: add a more detailed description, maybe a pointer to the docs on how to use MCP
+      .option("--mcp", "Run an MCP server")
   ).action(async (options) => {
     wrapCommandAction("dev", DevCommandOptions, options, async (opts) => {
       await devCommand(opts);

packages/cli-v3/src/dev/devSession.ts

@@ -23,6 +23,7 @@ import { logger } from "../utilities/logger.js";
 import { clearTmpDirs, EphemeralDirectory, getTmpDir } from "../utilities/tempDirectories.js";
 import { startDevOutput } from "./devOutput.js";
 import { startWorkerRuntime } from "./devSupervisor.js";
+import { startMcpServer } from "./mcpServer.js";
 
 export type DevSessionOptions = {
   name: string | undefined;
@@ -59,6 +60,16 @@ export async function startDevSession({
     dashboardUrl,
   });
 
+  if (rawArgs.mcp) {
+    await startMcpServer({
+      cliApiClient: client,
+      devSession: {
+        dashboardUrl,
+        projectRef: rawConfig.project,
+      },
+    });
+  }
+
   const stopOutput = startDevOutput({
     name,
     dashboardUrl,
@@ -190,6 +201,7 @@ export async function startDevSession({
       stopBundling?.().catch((error) => {});
       runtime.shutdown().catch((error) => {});
       stopOutput();
+      // TODO: stop MCP server
     },
   };
 }

packages/cli-v3/src/dev/mcpServer.ts

@@ -0,0 +1,82 @@
+import { McpServer } from "@modelcontextprotocol/sdk/server/mcp.js";
+import { SSEServerTransport } from "@modelcontextprotocol/sdk/server/sse.js";
+import { z } from "zod";
+import { logger } from "../utilities/logger.js";
+import { CliApiClient } from "../apiClient.js";
+import { ApiClient } from "@trigger.dev/core/v3";
+import polka from "polka";
+
+let projectRef: string;
+let dashboardUrl: string;
+// there is some overlap between `ApiClient` and `CliApiClient` which is not ideal
+// we can address in this in the future, but for now we need keep using both
+// as `ApiClient` exposes most of the methods needed for the MCP tools
+let sdkApiClient: ApiClient;
+
+let mcpTransport: SSEServerTransport | null = null;
+
+const server = new McpServer({
+  name: "trigger.dev",
+  version: "1.0.0",
+});
+
+server.tool(
+  "trigger-task",
+  "Trigger a task",
+  {
+    id: z.string().describe("The id of the task to trigger"),
+  },
+  async ({ id }) => {
+    const result = await sdkApiClient.triggerTask(id, {
+      // TODO: enable the user to pass in a custom payload
+      payload: {},
+    });
+
+    const taskRunUrl = `${dashboardUrl}/projects/v3/${projectRef}/runs/${result.id}`;
+
+    return {
+      content: [
+        {
+          type: "text",
+          text: JSON.stringify({ ...result, taskRunUrl }, null, 2),
+        },
+      ],
+    };
+  }
+);
+
+const app = polka();
+app.get("/sse", (_req, res) => {
+  mcpTransport = new SSEServerTransport("/messages", res);
+  server.connect(mcpTransport);
+});
+app.post("/messages", (req, res) => {
+  if (mcpTransport) {
+    mcpTransport.handlePostMessage(req, res);
+  }
+});
+
+export const startMcpServer = async (options: {
+  cliApiClient: CliApiClient;
+  devSession: {
+    dashboardUrl: string;
+    projectRef: string;
+  };
+}) => {
+  const { apiURL, accessToken } = options.cliApiClient;
+
+  if (!accessToken) {
+    logger.error("No access token found in the API client, failed to start the MCP server");
+    return;
+  }
+
+  sdkApiClient = new ApiClient(apiURL, accessToken);
+  projectRef = options.devSession.projectRef;
+  dashboardUrl = options.devSession.dashboardUrl;
+
+  // TODO: make the port configurable
+  const port = 3333;
+  app.listen(port, () => {
+    logger.info(`Trigger.dev MCP Server is now running on port ${port} ✨`);
+  });
+};