Pacioli

Least-privilege governance for ERPNext, and a governed agent front door built on top of it — MCP and A2A, one spine behind both. A door admits; it never decides.

In 1494, in Venice, Luca Pacioli printed the Summa de arithmetica — and inside it, the tract that taught the world double-entry bookkeeping. He wrote it down not because merchants couldn't count, but because they couldn't trust. His rule is one sentence deep: no debit without a credit. Every action gets an equal, opposite, recorded counterpart — and a book that doesn't balance confesses on the spot. Five hundred years of prove it or it didn't happen.

This repo is that tract, written again for a new clerk. The merchant's problem hasn't changed; the clerk has. He balanced books for merchants who couldn't watch every clerk. This balances them for owners who can't watch every agent. Same problem, five centuries apart. Same fix.

Tavola I — The friar at his slate, attributed to Jacopo de' Barbari, 1495. The glass rhombicuboctahedron hangs at his left; the Summa sits under the dodecahedron at his right. This repo's device is that hanging solid.

Distinctio I — Of the Two Instruments

There are two instruments in this house, and they compose — they do not couple. The first guards every credential on the site whether an agent is involved or not; the second is the one governed door an agent may use. The first is the floor; the second stands on it and submits to it. What follows is each instrument as the treatise would have it: what it is, what it refuses, and how it is installed.

The Guard — the counting-house door

No one writes in the books but the appointed hand, and only in the books appointed to them.

A Frappe/ERPNext bench app (distribution name pacioli-guard on PyPI; installs as the pacioli_guard bench app). It binds any API credential — an integration, a Zapier/n8n flow, a script, a vendor token, a cron job, an AI agent — to an allowlist of methods (and, if granted, DocTypes), enforced at the credential layer through Frappe's public auth_hooks extension point, deny-by-default. No core fork. It governs every credential on the site, agent or not.

# from your bench directory: wheel into the bench env, then install the app
env/bin/pip install pacioli-guard
bench --site  install-app pacioli_guard

The Broker — the governed front door

The clerk may propose; only the merchant disposes.

A standalone, pip-installable broker (pip install pacioli) that gives an AI agent a governed way to touch ERPNext — through the door of your choosing: MCP or A2A, one spine behind both. 51 governed doctypes, 265 tools — the full submittable transaction surface of an ERPNext company — every write through PLAN → CONSENT → execute → PROVE, deny-by-default beyond that. The door admits; the spine decides.

pip install pacioli

How the instruments compose

Guard is the floor; the broker is one consumer that binds itself to it. Guard scopes and enforces any credential on the site — you don't need to run an agent to need it. The broker is the agent-facing front door, and its own ERPNext credential must itself be pacioli_guard-scoped to exactly the calls it makes (the governed doctypes and their submit/cancel vectors — shipped as data lists the deploy kit applies). Without that scoping, anything holding the broker's raw credential can call ERPNext's REST API directly and bypass PLAN, CONSENT, and PROVE entirely — so the broker's own README states that scoping as a hard precondition, not an optional hardening step.

This is composition, not coupling: Guard is independently useful for any credential on a site, agent or otherwise; the broker is the one piece that chooses to sit on top of it and honor the same floor it enforces on everything else.

Distinctio II — Of the Memorandum, the Journal, and the Ledger

Double entry is not a metaphor here. It is the design. The bookkeeping tract of the Summa (Particularis de Computis et Scripturis) organizes a merchant's truth into three books, and slice for slice they are this system. In his journal every entry named its debit with per and its credit with a — nothing moved on one leg. Read the spread the way he ruled it:

| folio | per — his book (1494) | a — here | |---|---|---| | ¹ | The memorandum (memoriale) — every transaction written down first, roughly, before any formal entry | PLAN — plan_submit / plan_cancel write the memorandum: the projected GL and the risk flags, dated, bound to the draft. Nothing posts. | | ² | The journal (giornale) — each entry rewritten in fixed form, its debit marked per, its credit marked a | PROVE — the hash-chained receipt book. The intent receipt is the per, the outcome the a; an intent with no outcome is a debit with no credit, and the trial balance surfaces it as an orphan. | | ³ | The ledger (quaderno) — the book of account itself | ERPNext's GL — the broker never writes in it directly; every entry reaches the ledger through the journal's discipline. |

And the same law runs across every pillar — for every action, its recorded counterpart:

| folio | the action (per) | its recorded counterpart (a) | |---|---|---| | ⁴ | An agent wants to write | PLAN — the projected GL impact, written down before the act. The mirror entry precedes the entry. | | ⁵ | A plan exists | CONSENT — a human mints the marker, out of band. Agent proposes, human disposes: two hands on every posting, never one. | | ⁶ | The write fires | PROVE — an intent receipt before, an outcome receipt after. A write missing its outcome is an orphan, and it surfaces exactly the way an unbalanced trial balance does. | | ⁷ | A posting stands | UNDO — ERPNext's own cancel/amend is double-entry: the reversal posts equal-and-opposite rows. Nothing erased, everything answered. | | ⁸ | A credential exists | Guard — no capability without its explicit grant line. Deny-by-default is "no entry without authorization," applied at the credential layer. |

Same law at every layer: nothing moves without its counterpart. A plan without consent doesn't post. A write without a receipt is flagged. A credential without a grant is refused. The one system you can't trust is the one where an action can happen alone — unplanned, unconsented, unreceipted. Everything Pacioli refuses is exactly that: the lone entry.

Tavola II — Vigintisex Basium Planum Vacuum: the same solid, drawn hollow by Leonardo da Vinci for Pacioli's De divina proportione. Leonardo illustrated Luca's book; the debt is repaid here.

Distinctio III — Of the Counting-House Door

His counsel, applied at the credential layer:

• Two hands on every entry. The clerk writes; the merchant grants. The consent marker is

minted (pacioli mint) outside the agent's reach — no posting on one hand's authority.

• The counting-house door. No one writes in the books but the appointed hand, and only in

the books appointed to them — that is Guard, per-credential and per-doctype, deny-by-default.

• The registered book. The books take their authority from a mark held outside the

bookkeeper's own hand. pacioli anchor carries the receipt-book's head off the box — a registration the book cannot rewrite, so a truncated or swapped book confesses against it.

Distinctio IV — Of the Closing of the Books

> ❧ Do not go to sleep until the debits equal the credits.

He gave merchants that rule, and it is the operating rule here too. pacioli verify is that sleep test — run the trial balance, and if intent and outcome don't pair, the book itself tells you.

The closed books. Closing the ledger is his own operation: rule off the book, carry the balances forward. The broker refuses to write in a closed book — a closed Accounting Period, a Period-Closing-Voucher boundary, a frozen-books date — and never slips a backdated or future-dated entry past the ruling-off.

Distinctio V — Of the Inventory

Open no books before the survey. He starts the merchant with a complete inventory before a single entry — what you hold, what is owed, what is missing. pacioli doctor is that survey for this house: what is reachable, what is granted, what refuses and why — and the road does not proceed until the doctor says ready. The census (pacioli close) then keeps the inventory honest for every period after: statement, reconciliation, response — every finding accounted for, or the book says so out loud.

Status

(Current versions live in each package's pyproject.toml/CHANGELOG.md — this README deliberately does not restate them.)

Guard — deny-by-default credential scoping with the deny-unknown posture (an unrecognized generic RPC is denied even if granted; per-doctype grants + three curated safe methods are the whole surface), live-proven on a real Frappe v16 bench (Gates 1, 7, 10).

Broker — 51 governed doctypes, 265 tools; 38 of the 51 live-proven end-to-end on a real ERPNext v16 bench as a guard-scoped seat (Gates 2–10, envelopes E1–E8, and the 2026-07 live-prove sweep): governed submit/cancel/amend across accounts, stock, assets, manufacturing, and subcontracting; Workflow-SoD consent; cascade cancel with dependent graphs (a 3-node Asset graph under one consent, live); governed Payment Reconciliation (stricter than ERPNext itself — the closed-books belt ERPNext skips for reconciliation, proven live, PHASE X); the armed-Budget control-plane probe (arm → the bench refuses the PO → disarm → the same PO passes, every step disclosed pre-consent); the off-box anchor; a certified least-privilege reference seat; and the founding refusals (no debit without a credit — live). The whole arc is written up leg-by-leg in [SCOPED-TOKEN-PROOF.md](./SCOPED-TOKEN-PROOF.md) (PHASES A–X). See [broker/README.md](./broker/README.md#honest-scope) for exactly what ships and what doesn't.

License

Apache-2.0.

Here ends the Summa of Governance: printed upon the counsel of Fra Luca Pacioli, who taught that no entry stands alone; set in these types for the governance of agents upon the books.

VENETIIS MCDXCIV · IN THE WORKSHOP OF JOHN BROADWAY · MMXXVI

Source & license

This open-source MCP server is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: john-broadway
• Source: john-broadway/pacioli
• License: Apache-2.0

Install and usage instructions live in the source repository linked above.