Claude Code Setup

Connect Massive to Claude Code with the remote MCP server

Massive's remote MCP server connects Claude Code to live U.S. market data: dividends, trades, quotes, options chains, and the rest of our catalog. It queries our REST API under the hood, giving Claude Code the context to pull that data directly and write correct code against it.

This guide walks through connecting the remote MCP server, authenticating over OAuth, and verifying the integration. Setup takes about two minutes and requires Claude Code installed plus a Massive account. There is nothing else to download, and authentication happens in your browser. It then covers the optional Massive plugin, which teaches Claude Code to write correct code against our API.

What You Can Do

Once connected, the MCP server gives Claude Code a small set of composable tools for endpoint search and live API calls, so you can ask it to:

  • Pull every dividend declared this month across U.S. stocks and rank them by yield.
  • Inspect the live response shape of an endpoint before writing code against it.
  • Build a Python project that screens options chains, then verify it against real API responses.
  • Figure out which Massive endpoint returns the data shape you need.

Because the server runs the calls itself, Claude Code can check real responses while it works, which is useful for confirming response shapes or chasing down a hallucinated field name.

Setup

Two steps. Allow about two minutes start to finish.

1. Install Claude Code

If you don't have it, install Claude Code and confirm it works:

claude --version

2. Add the Massive Remote MCP Server

Register the remote server with Claude Code:

claude mcp add --transport http massive https://mcp.massive.com/

Then launch Claude Code and authenticate:

  1. Run claude
  2. Type /mcp
  3. Select massive
  4. Select 1. Authenticate and complete the sign-in in your browser

Authentication uses OAuth against your Massive account, so there is no API key to copy or store. A free Basic account is enough to start.

Your MCP access mirrors your Massive entitlements. You can query any asset class your plan includes. If you have Stocks access, stocks data is available through MCP. Requesting data you are not entitled to (for example, Options without an Options plan) returns an access-denied error.

Test the Integration

Now that the connection is live, put it through its paces. A few prompts to start with:

  • "Show me the latest trade for AAPL." (Trades)
  • "Is the U.S. market open right now?" (Market Status)
  • "When is the next market holiday?" (Market Holidays)
  • "What dividends has AAPL paid this year?" (Dividends)
  • "Give me a snapshot of today's biggest gainers." (Snapshots)

When you're ready to go deeper, hand Claude Code a full brief and let it chain several calls together:

Pull all dividends declared in the last 30 days, filter to U.S. stocks with a market cap over $50 billion, rank them by yield, and summarize the top five with their pay dates.

Claude Code will search for the right endpoints, make the live calls, and stitch the results into a single answer.

Add the Massive Plugin

The MCP server gives Claude Code live data. The Massive plugin teaches it how to write correct code against our API: the right host and auth, when to use REST, WebSocket, or Flat Files, what your plan includes, and how to get accurate historical numbers from adjusted prices, point-in-time data, and delisted tickers. It also adds recipes for backtests, screens, options chains, earnings prep, market briefs, and live streams.

The plugin is open source at github.com/massive-com/ai.

1. Set Your API Key

The code the plugin writes calls the REST API directly, so it reads your key from the MASSIVE_API_KEY environment variable. Find your key in the Dashboard and export it before you start Claude Code:

export MASSIVE_API_KEY=your_key_here

The command above saves your key in your shell history. To keep it out, run the command below instead. Paste your key and press Enter. Nothing appears as you paste.

read -s MASSIVE_API_KEY && export MASSIVE_API_KEY

2. Install the Plugin

In Claude Code, run:

/plugin install massive --marketplace massive-com/ai

On Claude Code older than 2.1.275, add the marketplace first:

/plugin marketplace add massive-com/ai
/plugin install massive@massive-plugins

Restart Claude Code to load the skills.

How the Plugin and MCP Server Fit Together

Each one works without the other, and they do different jobs:

  • The MCP server runs lookups inside your session. Claude Code calls its tools to find an endpoint and fetch live data. It signs in with OAuth.
  • The plugin shapes the code Claude Code writes for you. That code calls the REST API with MASSIVE_API_KEY, so it runs on its own after the session ends.

The plugin does not install the MCP server. When both are present, Claude Code uses the MCP server for quick lookups during the session and still writes REST code for anything you ship.

Troubleshooting

massive doesn't appear under /mcp. Confirm the server was added with claude mcp list. If it's missing, run the add command from Step 2 again.

Authentication didn't complete. Run /mcp, select massive, and choose Authenticate again. Make sure you finished the browser sign-in and granted access.

Claude responds with numbers but doesn't cite an MCP call. It's answering from training data. Ask it explicitly to use the Massive tools, e.g. "use the Massive MCP server to check."

Numbers look wrong or made up. The server likely isn't connected. Confirm with claude mcp list and that /mcp shows massive as connected and authenticated.

The plugin's skills don't load. Restart Claude Code after the install. Run /plugin and confirm massive is installed and enabled.

Code from the plugin fails with an authentication error. MASSIVE_API_KEY isn't set in the shell that started Claude Code. Export it, then restart Claude Code.

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