teller MCP server

The teller MCP server gives agents read-only access to the user’s bank data through Teller. One server, but it routes across multiple enrollments — the user can connect N banks; the agent dispatches per-call by enrollment_id.

Injected only when the user has at least one Teller integration granted to the running profile.

Tools

`teller_list_enrollments`

{}

Returns one line per connected bank: enrollment_id, institution name, linked: <date>. Call this first to discover what’s available.

`teller_list_accounts`

{ "enrollment_id": "enr_…" }

Returns accounts for one enrollment: account_id, name, type, subtype, currency, last_four, institution. Use the account_id with the per-account tools below.

`teller_get_balance`

{ "enrollment_id": "enr_…", "account_id": "acc_…" }

Returns available and ledger balances for one account.

`teller_list_transactions`

{
  "enrollment_id": "enr_…",
  "account_id": "acc_…",
  "count": 50,
  "from_id": "txn_… (optional, paginate older)"
}

Recent transactions newest-first. Default count=50, max ~250 (Teller’s limit).

Preferred for budgeting / spend categorization — it’s a flat $0.30/enrollment/month subscription on Production, not per-call.

`teller_get_account_details`

{ "enrollment_id": "enr_…", "account_id": "acc_…" }

Account number + routing numbers. Sensitive — call only when explicitly relevant (bill payment, ACH setup). Most expensive endpoint on Production: $1.75/call (Identity tier). Never speculate on this one.

Authentication

Authorization: Bearer teller_<token>. The bearer carries { userId, profileId }. The server uses profileId to filter enrollments — only ones granted to this profile are visible. A leaked token can’t reach an enrollment that wasn’t scoped to its profile.

mTLS

Teller requires mutual TLS on every API call. Vonzio handles the cert exchange server-side — you don’t need to provision anything to use the integration.

Environment

Three modes:

`TELLER_ENVIRONMENT`	What
`sandbox` (default)	Fake test banks. The PNC sandbox accounts work for development. No real money.
`development`	Real banks, real accounts. Free tier, capped at 100 connections. Recommended for personal use.
`production`	Paid tier. Per-call billing as described above. Required for shipping a multi-user product.

The dashboard widget honors whichever the server announces via /v1/integrations/teller/config.

Caching

The MCP keeps a per-token TTL cache of “this user’s enrollments” (30s) so chatty agents don’t re-decrypt the integration rows on every tool call. Cache invalidates with the token’s task lifetime; you don’t manage it.

Token-cost guidance in the tool descriptions

The tool descriptions themselves tell the agent the cost trade-offs. Agents that read tool descriptions before choosing a tool (most LLMs do this implicitly) get cost-aware behavior for free. See feature #16 (cost hints) for the wiring.