--- title: "How do I use FundFacts API with Claude Code?" description: "Register the FundFacts MCP server with claude mcp add or install the plugin, sign in with /mcp, then add AGENTS.md so Claude Code looks up real funds and builds screeners, reports or bots on the API." canonical: https://fundfactsapi.com/answers/fund-data-for-claude-code published: 2026-09-12 updated: 2026-10-13 publisher: FundFacts API --- # How do I use FundFacts API with Claude Code? **Short answer:** Register the FundFacts MCP server with claude mcp add --transport http fundfacts https://fundfactsapi.com/api/mcp, then run /mcp to sign in with your FundFacts account (or add --header "Authorization: Bearer ffk_..." to use an API key); the FundFacts plugin does the same and adds four skills. Claude Code can then look up and compare real funds while it works. Add the companion kit's AGENTS.md (or the public edition from /llms-full.txt) at the project root, and a prompt such as "build a fund comparison page for a list of ISINs" produces working code against the API. **Start with the MCP server.** One command (or the plugin) gives Claude Code seven read-only fund tools on every FundFacts plan, Free included; in the terminal the results come back as text. The [MCP server guide](https://fundfactsapi.com/docs/mcp) has the tool reference and troubleshooting. ## Three pieces, each optional **AGENTS.md** is the one that matters most. It is a complete, current description of the API written for coding agents: endpoints, the response envelope, every field of `data` with type and example, the quota rules, error handling, and a reference client in TypeScript and Python. Claude Code reads it at the start of a session. The public edition is at [/llms-full.txt](https://fundfactsapi.com/llms-full.txt); subscribers download a version with their plan limits and key from the dashboard. ```bash # public edition, no key inside curl -s https://fundfactsapi.com/llms-full.txt -o AGENTS.md ``` **The skill** (`.claude/skills/fundfacts-api/SKILL.md` in the kit) tells Claude Code when to reach for the API and how to structure fund-data code: cache by ISIN until `expiresAt`, 300-second timeouts on `/funds/{isin}`, never ship the key to a browser bundle, show `dataAsOf`. **The MCP server** lets Claude Code *look at real data* while it codes: check a field name, test an ISIN, see what a bond fund's payload contains before writing the parser. ```bash claude mcp add --transport http fundfacts https://fundfactsapi.com/api/mcp ``` Then run `/mcp` in a session and sign in with your FundFacts account; the connection appears in the [dashboard](https://fundfactsapi.com/dashboard), where you can disconnect it. To use an API key instead, add `--header "Authorization: Bearer ffk_..."` to the command. Or install the FundFacts plugin (public repository: github.com/fundfactsapi/fundfacts-plugin), which adds the server together with four skills that tell Claude Code how to read the fund data: `/plugin marketplace add fundfactsapi/fundfacts-plugin`, then `/plugin install fundfacts@fundfacts`, then `/mcp` to sign in. ## Prompts that work - "Using AGENTS.md, build a Next.js page that takes a list of ISINs and shows name, TER, risk indicator and 5-year annualised return in a table, cached in Postgres until expiresAt." - "Write a Python script that loads isins.csv through POST /funds in batches of 50, retries pending ISINs after 60 seconds, and writes name, category, TER and AUM to a parquet file." - "Add a Slack bot command /fund that replies with the top five holdings and the sector split." The [guide to building a fund app with a coding agent](https://fundfactsapi.com/blog/build-fund-app-with-ai-coding-agent) walks through a full session. ## Rules the agent should follow The kit spells these out; they are worth knowing because they explain the code Claude Code writes: 1. Read the key from `FUNDFACTS_API_KEY`; never commit it. 2. Cache by ISIN with `expiresAt`; stop before `X-RateLimit-Remaining` hits zero; sleep `Retry-After` on 429. 3. Timeout of 300 seconds on the single-fund endpoint; a loading state in UIs for cold ISINs. 4. Retry only `502 upstream_error`, at most twice; never retry 4xx. 5. Treat `404 fund_not_found` as "not a covered fund", not a bug. 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](https://fundfactsapi.com/llms-full.txt). ## FAQ ### Which plan includes the kit? Starter ($9.99) and above. The public AGENTS.md at /llms-full.txt has the same reference minus your key and plan limits, so you can start on the Free plan and switch later. ### Do I need a credit card to try it? No. The Free plan is 5 lookups per month with no card; sign up with an e-mail address or Google and the key is shown in the dashboard. ### Which ISINs work? Any share class of a UCITS fund, ETF, money-market fund or open-end fund whose management company publishes a product page, factsheet and KID. Each share class has its own ISIN and is looked up on its own. Stocks, bonds and indices are not funds and return 404 fund_not_found. ## About FundFacts API FundFacts turns any fund or ETF ISIN into one dated factsheet (fees and KID costs, the 1–7 risk indicator, holdings, sector and country exposure, returns) read from the fund house's own documents: as a client-ready PDF under your firm's name for advisers and wealth managers, as JSON through its API for developers, or inside ChatGPT and Claude through its MCP server. FundFacts works inside ChatGPT and Claude as a connector (a remote MCP server): ask about any fund or ETF by ISIN, ticker or name and the assistant answers from FundFacts' dated figures, fees, risk, holdings, exposure and returns, with fund cards, side-by-side comparisons, holdings overlap and portfolio look-through. - Free API key, no card: https://fundfactsapi.com/signup - Documentation: https://fundfactsapi.com/docs (OpenAPI: https://fundfactsapi.com/openapi.json) - MCP server: https://fundfactsapi.com/api/mcp (set-up for every client: https://fundfactsapi.com/mcp-server) - Pricing: https://fundfactsapi.com/pricing - Site index for AI assistants: https://fundfactsapi.com/llms.txt - Informational data, not investment advice.