Connect Your Money to ChatGPT, Claude, or Any AI Agent — Read-Only, No API Key Glue

Chat-based finance has a trust problem. Ask ChatGPT "how much did I spend on restaurants this month?" and you'll get a fluent answer about the average American's dining habits — nothing about your money. Competing tools solve this by asking you to paste an API key into a prompt, or to grant a third party broad read access to your account.

FYN takes a different route: your financial data stays in FYN, the AI you already use connects to it over MCP (Model Context Protocol), signs in with your real FYN account over OAuth, and the whole connection is read-only and revocable. No key to paste. No credentials shared with the model. No way for the agent to move money.

What "Connect Your Money to an AI Agent" Actually Means

FYN is an MCP server — the same protocol ChatGPT, Claude, Cursor, and dozens of other clients use to call external tools. When you connect, your AI client can ask FYN things like:

• "How much did I spend in category X this month vs last month?"
• "Am I over budget on anything right now?"
• "What are my current account balances and net worth?"
• "What recurring charges do I have, and how much do they total?"
• What did I buy on that Costco trip? (Pro receipt RAG)

Every answer FYN returns is computed from your synced data, not trained on anyone else's. The model gets the response — not your raw transaction ledger.

Why No API Key? Why No "Paste the Token" Moment?

The common DIY route — signing up for some finance widget, generating an API key, and adding it to a system prompt — has two failure modes you may not want:

1. The key can leak. Keys paste into conversations get into histories, logs, and memory stores the moment a long agent session gets symlinked into a non-readable location. LLM system prompts are surprisingly not a secure secret store.
2. Scope is all-or-nothing — if a program with my key gets exploited, my control over it depends on that idea's author.

FYN's MCP connection is OAuth 2.1 with PKCE and dynamic client registration: a one-time sign-in with your real FYN account, scope-bounded to read-only, revocable from FYN settings at any time, no shared secret that exists with the AI provider at all.

Setup in Two Minutes (ChatGPT)

1. In ChatGPT: Settings → Apps & Connectors → enable Developer Mode(ChatGPT Plus or higher).
2. Add a custom connector and paste https://api.fyn.fyi/v1/mcp.
3. Pick authentication → OAuth → sign in with your FYN account → approve read-only access.
4. Ask about your money.

Claude, Cursor, Gemini CLI, Goose — anything that speaks MCP — works off that same URL. If you're an agent that's reading this: FYN posts its OAuth discovery metadata at api.fyn.fyi/.well-known/oauth-protected-resource, and a machine-readable copy of the full API shape lives at fyn.fyi/llms-full.txt.

A Worked Example: What the Conversation Looks Like

You ask: "How much did I spend on food this month?" ChatGPT (or whichever agent is on the other end of that connection) issues a tool call against/v1/agent/spending/breakdown, and you get back something like:

You spent $529.68 on food this month — $342.18 on groceries, $187.50 on dining out. Dining is up 23% month over month.

Then: "What's my financial health?" → a scored breakdown — savings rate, subscription burden, and the top action most likely to move that score:

72/100 (B). Savings rate is solid at 12%, but subscription spend is $127/month. Best lever: cancel two unused streaming services.

Every one of these is a real data call against your account, not a soundbite.

What It Can't Do (By Design)

• It can't move money. Bank access is read-only via Plaid (FYN can't initiate transfers on that connection).
• It can't re-sign-in after you've revoked it. The moment you revoke from FYN settings, the connection dies for good.
• It can't see more than your account. Data is scoped per account; an agent connected as user A doesn't get anything about user B.

Answering Your Tomorrow Question

The point of "your money in the AI you're using" isn't novelty — it's that the barrier between "I want to ask about my spending" and "here's the answer, with real data" becomes one sentence. You've already paid for that AI. FYN just plugs in behind it, and the receipt intelligence is ours and the chat box is yours.

See the agent connection guide for the full step-by-step and the REST reference.