Claude Code and Codex plugin
Install Probably's plugin for Claude Code, or its skills for Codex: recipes for testing hooks, turning an ad into a brief, research and scripts, and checking on videos.
Probably's plugin brings its MCP server and a set of recipes to Claude Code, and the same recipes to Codex as skills. A recipe is a skill that knows the flow for one job, such as testing five hooks for a product, and follows the spend rule on every paid step: it shows you the preview and waits for your yes before it confirms anything.
Install in Claude Code
Add Probably's marketplace and install the plugin:
claude plugin marketplace add probablyco/probably-plugins
claude plugin install probably@probablyIn a Claude Code session, /plugin marketplace add and /plugin install do the same. The plugin adds the MCP server at https://studio.probably.co/api/mcp; run /mcp, choose the plugin's probably server and authenticate. Your browser opens Probably's sign-in and a consent page, where you choose the organization, optionally one Space, and whether Claude Code may start paid work after you confirm it in the chat.
With an API key instead
Where nobody can open a browser, add the server yourself with a key from Settings → Connections (see Authentication); the recipes work with either server:
export PROBABLY_API_KEY="prb_..."
claude mcp add --transport http probably https://studio.probably.co/api/mcp \
--header "Authorization: Bearer $PROBABLY_API_KEY"The plugin's own server then stays signed out, and you can disable it in /mcp. A key that may spend must be limited to one Space with a spend cap.
Add the skills to Codex
Codex reads skills from ~/.agents/skills, and follows symlinks there. Clone the plugin's repository once and link its skills, so an update is one pull:
git clone https://github.com/probablyco/probably-plugins ~/.probably-plugins
mkdir -p ~/.agents/skills
ln -s ~/.probably-plugins/probably/skills/* ~/.agents/skills/git -C ~/.probably-plugins pullThen connect Codex to the MCP server, if you haven't, and sign in:
[mcp_servers.probably]
url = "https://studio.probably.co/api/mcp"codex mcp login probablyTo use an API key from an environment variable instead, follow the Codex quickstart.
The recipes
Ask in plain words, or name a recipe (in Claude Code, /probably:test-hooks; in Codex, $test-hooks):
| Recipe | Ask | What it does |
|---|---|---|
probably | "What can Probably do for me?" | The reference the others build on: reaching the tools, the spend rule, request keys and refusals. |
test-hooks | "Test 5 hooks for this product." | Drafts hooks for you to edit, makes a source video, then prepares one variant per hook that keeps its research. |
ad-to-brief | "Turn this winning ad into a brief." | Reads the link with read_link, writes a brief that borrows its hook or pacing without copying it, and prepares the video. |
research-then-script | "Research this product, then write a script." | Runs research, brainstorm (you pick the hooks), write_script at your length and review, reading each with get_stage. |
check-videos | "How are my videos doing?" | Lists what waits on you first, then what is in production and what is delivered, and waits for changes when you ask. |
Every recipe discovers the server's tools before it calls them, so it uses what your server offers today. Paid work only ever starts through confirm_spend, after you agree to its preview (see Spend confirmations).