Massive Market Data Codex Plugin

A Codex plugin for building and debugging integrations against the Massive market data API. You get five workflow skills, the Massive API knowledge file, and the Massive MCP server — all in one install.

What you get

Five skills for common integration tasks:

• massive-scaffold — new Massive project with SDK dependencies, .env, and working boilerplate
• massive-discover — find the right endpoint, parameters, plan tier, and SDK example for a data task
• massive-debug — diagnose API errors, empty results, rate limits, and SDK misuse
• massive-options — options strategies and analysis using Massive options data
• massive-dashboard — scaffold a Streamlit dashboard backed by Massive APIs

An AGENTS.md knowledge file covering ticker formats, SDK naming, pagination, auth, plan tiers, and the common pitfalls.

The Massive MCP server, bundled via uvx. It exposes three tools to Codex: search_endpoints, call_api, and query_data. Codex uses them for live endpoint discovery, API calls, and SQL over stored DataFrames. If the server can't launch, the skills fall back to AGENTS.md and say so.

Install

Three steps. No restarts.

Before you start

• OpenAI Codex CLI drives the two codex commands below. Install with npm install -g @openai/codex or brew install codex. Runs on macOS, Windows, and Linux.
• OpenAI Codex desktop app is where you install the plugin and chat. Available on macOS and Windows from developers.openai.com/codex. Linux users can use the Codex TUI (codex) instead — see the note at the end.
• uv launches the bundled MCP server. Install with curl -LsSf https://astral.sh/uv/install.sh | sh (macOS or Linux), powershell -c "irm https://astral.sh/uv/install.ps1 | iex" (Windows), or pip install uv (any platform). Python 3.12+ is fetched automatically by uvx on first MCP launch.
• A Massive API key. The free Basic tier is enough to start.

1. Add the marketplace

codex plugin marketplace add massive-com/codex-plugin

For local development from a checkout of this repo, use codex plugin marketplace add . instead.

2. Install the plugin from the Codex app

Open the Codex desktop app, go to the plugins screen, find Massive Market Data in the drop down, and Install or add it to Codex.

3. Register your API key if using the MCP server.

codex mcp add massive --env MASSIVE_API_KEY=YOUR_MASSIVE_API_KEY -- uvx --from git+https://github.com/massive-com/mcp_massive mcp_massive

This writes a user-level entry to ~/.codex/config.toml that overrides the plugin's placeholder with your key. The next chat you start will pick it up — the MCP list in the app may not refresh until you reopen the application the next time, but calls from chat work right away. Rotate later with codex mcp remove massive followed by the same add command with the new value.

If you'd rather keep the key in your shell environment, skip this step. The bundled MCP reads MASSIVE_API_KEY via env_vars. For the macOS desktop app, run launchctl setenv MASSIVE_API_KEY your_key so the GUI inherits the value.

Linux (TUI) users: after step 1, run codex, type /plugins, install Massive Market Data, then /exit to leave cleanly before running step 3.

Verify

codex mcp list

Should show massive as enabled. In the Codex app, start a new chat and try:

Use $massive-discover to find the right Massive endpoint for daily AAPL aggregates in Python.

If the MCP is working, Codex will call search_endpoints against the live server. If it isn't, the skill falls back to AGENTS.md and tells you so.

Accuracy model

AGENTS.md holds stable facts (ticker formats, SDK conventions, plan tiers) that don't change often. The MCP server is the source of truth for live endpoint metadata, parameters, and response shapes — skills prefer it over memory. When live lookup fails, skills are expected to say so, not invent routes or fields. Skill names are prefixed massive- to avoid collisions with generic skills from other plugins.

Local development

Codex caches an installed copy of the plugin rather than reading your working tree. If you edit skills, manifests, or other install-surface files, bump the version in plugins/massive/.codex-plugin/plugin.json and reinstall via /plugins. That's the reliable way to get Codex to pick up your changes.

License

MIT.

Disclaimer

Educational material, not investment advice or a recommendation to buy or sell any security. Massive is a market data provider, not a broker-dealer, exchange, or investment adviser. Market data may originate from third-party exchanges and data providers, or may be derived or calculated by Massive; in either case, it is subject to the terms of your Massive subscription. The data and code samples are provided as-is, without warranty of accuracy, completeness, or timeliness. You're responsible for your use of the data and for compliance with all applicable laws and data licensing terms.