How to add Locus MCP to Codex CLI and app

Setup, step by step

1. Step 1

   Create a Locus Pro account

   Sign up at paywithlocus.com/pro. The Free plan has no subscription. Paid calls use prepaid credits.

2. Step 2

   Add the Locus marketplace

   Run this in a terminal with the Codex CLI installed.

   codex plugin marketplace add locus-technologies/locus-pro-plugin

3. Step 3

   Install the Locus plugin

   This adds the MCP server https://api.paywithlocus.com/api/credits/mcp and the locus, locus-setup, and locus-workflows skills.

   codex plugin add locus@locus

4. Step 4

   Sign in with OAuth

   Run the login command, then approve Locus in your browser. Choose a company if prompted.

   codex mcp login locus --scopes mcp:read,mcp:execute,offline_access

5. Step 5

   Confirm the saved server

   Codex should list the locus server with the production URL. The source header may read open-plugin. That is a Codex rewrite and is harmless.

   codex mcp get locus

6. Step 6

   Start a new session and check

   Start a new Codex CLI or desktop session so the tools load. Ask: What’s my Locus balance?

Should I use the plugin or add the MCP server alone?

Use the plugin. It installs the MCP server and all three skills in one step, and it is the path we tested end to end in the Codex CLI and desktop app.

If you only want the tools, add the server by hand. Codex stores MCP servers in ~/.codex/config.toml, which the Codex CLI, desktop app, and IDE extension share. The IDE extension does not install plugins, so run the plugin commands from the CLI.

How do I fix a Codex MCP login error?

Run codex mcp login locus again with the same scopes and finish the browser approval. Most failures are an approval tab that was closed or timed out.

If you added Locus by hand before, you may have two entries. Keep one so Codex does not load duplicate tools.

• Remove an old manual entry: codex mcp remove locus-pro
• Reset the token: codex mcp logout locus, then log in again
• Check the URL is https://api.paywithlocus.com/api/credits/mcp with codex mcp get locus
• Start a new session after any change. Running sessions keep the old tool list.

What can Codex do after Locus is connected?

Codex can search the Locus catalog, read an endpoint schema and price, and run the call against your credit balance. There is no separate account or API key per provider.

The core tools are search_apis, describe_api, estimate_cost, execute, get_call_result, and get_balance. The skills teach Codex when to use them, and locus-workflows lets it save repeatable multi-step runs.