Mercury integration

What it gives Plexward

Balance per account, so a finance brief can state cash on hand.
Recent transactions for reconciliation questions and for spotting a charge nobody recognizes.
Context for the monthly close, where the agent is preparing a summary rather than moving money.

Layer

account. One Mercury connector per Claude account.

{ "name": "Mercury", "layer": "claude.ai", "svc": "Banking", "account": "Acme accounts" }

Prerequisites

A Mercury account and the authority to connect it.
The connector attached on claude.ai.
A deliberate decision about what the agent may see. This is bank data: treat every output as sensitive and keep it out of shared documents.

Setup steps

Attach the connector on claude.ai and authorize.
Confirm from the brain: claude mcp list | grep -i mercury.
Declare it in catalog/declarations.json.
Write the sensitivity rule into the brain's routing doc, explicitly.

Per-entity routing

## Owned Integrations
| MCP Tool | Service | Account | Notes |
|---|---|---|---|
| Mercury | Banking | Acme accounts | Account layer. **Read only. Never write balances or transactions into a tracked file, a digest, or any shared surface.** |

## NOT This Company
- Mercury, in any entity that does not bank on this account.

That bracketed sentence is not decoration. Briefings get committed to brain repos and pushed to a remote. Bank figures do not belong there.

Verify

cd ~/brains/acme-brain && claude mcp list | grep -i mercury

Expected ✔ Connected. Then read a balance in a session and confirm it matches the app. Do not paste the result anywhere.

Common failures

Long-lived silent expiry, the same failure mode as Stripe. Probe on a schedule.
Read-only by design, and people expect otherwise. It is a reporting connector, not a payments rail.
Data leaking into a committed brief. The most likely real harm from this connector is not a breach, it is a number in a markdown file that gets pushed. Enforce it in the routing doc and check your digests.

What Plexward does with it once connected

A finance-oriented brief can state cash position and notable transactions in the session, on demand. Nothing is written to disk by default, and nothing is sent to a chat surface unless you ask for it in that moment.

Mercury