How do I use FundFacts API with OpenAI Codex?

AGENTS.md is the whole setup

Codex's convention is a file called AGENTS.md that it reads before working in a repository. The FundFacts kit produces one: a complete description of the API (endpoints, response envelope, every data field with type and example, quota and error rules, a TypeScript and Python reference client) that stays in sync with the live field reference. The public edition is at /llms-full.txt:

bash
curl -s https://fundfactsapi.com/llms-full.txt -o AGENTS.md

If your repository already has an AGENTS.md, append the FundFacts one under its own heading; Codex reads the whole file.

Live data through MCP

Codex CLI reads MCP servers from ~/.codex/config.toml:

toml
[mcp_servers.fundfacts]
url = "https://fundfactsapi.com/api/mcp"
bearer_token_env_var = "FUNDFACTS_API_KEY"

Export FUNDFACTS_API_KEY=ffk_... in the shell that launches Codex. The MCP server exposes six tools, each counted like the REST endpoint it wraps: get_fund (ISIN → the full factsheet payload), search_funds (name → ISINs, free), compare_funds (side-by-side table for several ISINs), analyze_portfolio (weighted look-through of a list of positions, Pro and above), fund_overlap (shared holdings between funds, Pro and above) and get_scpi (French SCPI data by name or ISIN). Authentication is the same bearer API key as the REST API, sent as an Authorization header. With the tools available, Codex checks a real payload before writing a parser instead of guessing field names.

Prompts

• "Following AGENTS.md, write a FastAPI service with GET /funds/{isin} that proxies FundFacts, caches in SQLite until expiresAt and strips everything except name, TER, risk and top holdings."
• "Load the ISINs in universe.txt with POST /funds in batches of 50 and produce a CSV of category, TER, AUM and 3-year volatility."

Paid plans include an AI companion kit generated from the live field reference: an AGENTS.md with every endpoint, field, rule and a reference client; a Cursor rule; a Claude Code skill; the OpenAPI spec and TypeScript types, with your key baked in or read from an environment variable. Download it from the dashboard; the public edition without a key is at /llms-full.txt.