Did we forget to bill anyone?
One order shipped and was never invoiced, and $1,700 of goods arrived that no supplier has billed yet. The order carries delivered and invoiced quantities, and the goods sit in the GRNI account until a bill clears them.
Open sourceApache 2.0Self-hosted
Purchasing and stockyour AI can't fudge.
OpenERP is an open-source ERP with an MCP server. Purchasing, stock and sales post to a double-entry ledger. A bill that doesn't match its order and the goods received is refused, and stock can't go below zero.
Explore the demoSample business, no sign-up
The demo app is part of a deployment Attri runs for you. The MCP server and the SQLite database are the open-source repo.
Ask the records what your agents did.
Nobody checks every order an agent raises. In OpenERP, every document posts as it happens, so the records answer these three questions.
What stops a bill that doesn't match?
The three-way match. A bill must agree with the purchase order on price and with the goods received on quantity, or it's refused with every discrepancy listed and nothing written.
Why do we only have 53?
Every stock move names the document behind it. Two brackets were written off after a count, with the reason, and their cost moved to expenses in the same transaction.
How it works
Your agent raises the documents.OpenERP decides whether they post.
Agent requests
- Order 100 bracketscreate_purchase_order
- Receive 90 of themreceive_goods · partial
- Bill for all 100post_vendor_bill · refused
- Ship 25 to Rivet & Codeliver_goods
- Import from your ERPNot built yet · Tell us you need it
OpenERP
Checks every document
- Bill matches order and receipts
- Stock never below zero
- Debits equal credits
- Audit row, same transaction
Stock value = Inventory account
create_purchase_order · PO-0004 · $1,800.00
Read back as
- JournalEvery line names its document
- Stock valuationAverage cost, per item
- Unbilled receiptsReceived, not yet billed
- Audit logEvery change, append-only
Claude reads them through the same 47 MCP tools it writes with. Read-only SQL covers anything else.
- 01
Raise
Your agent creates the order, receipt, bill or delivery. Partners and items resolve by code or name, so it can pass "Northwind Components" or "SKU-100" directly.
- 02
Check
The server runs the rules before anything is written: the three-way match on bills, the stock floor on deliveries, the balance on every journal entry. A failure returns the reason and writes nothing.
- 03
Post
The document, its stock moves, its journal entry and its audit row commit in one transaction. A posting is never edited; reverse_entry adds a contra entry instead.
Compared with an ERP behind a connector
Connectors decide who may write.OpenERP decides what can post.
An MCP connector puts your agent in front of an ERP built for people clicking through forms. The call goes through, with whatever checks that system has switched on.
An ERP behind an MCP connector
Your agent calls someone else's API
Controls who may writeAPI keys, roles and approval steps decide which agent can call which method.
Matching is a policyBilling against ordered rather than received quantities is a setting an admin can choose.
Negative stock is a settingSome ERPs let stock fall below zero so entries can be caught up later.
Often copyleftMany open-source ERPs ship under GPL or AGPL, which some regulated buyers' legal teams rule out.
OpenERPThe rules sit in the write path
Controls what can be writtenA bill that disagrees with its order or the goods received is refused, whichever agent sends it.
Matching blocks the billPrice against the order, quantity against receipts. Every discrepancy comes back at once, and nothing posts.
Stock can't go below zeroA delivery or write-off larger than what's on hand is refused with both numbers.
Apache 2.0A patent grant, and no copyleft terms on the code you build around it.
Use cases
For any team letting agents touch operations.Wherever a number might be questioned later.
Sample: a parts distributor
Agents raise the orders. The bills have to match.
Purchase orders, receipts and supplier bills raised by agents. A bill posts only when its price matches the order and its quantity matches what arrived.
- Three-way match on every vendor bill
- Every discrepancy listed in one refusal
- Goods received but not billed, as one balance
Sample: one warehouse, three products
Stock that can't go below zero, and a reason for every move.
Receipts, deliveries and count adjustments, each one a stock move at average cost that names the document behind it.
- Deliveries refused when stock runs short
- Write-offs carry a reason and post their cost
- Stock value always equals the Inventory account
Sample: two wholesale customers
Find what shipped and was never invoiced.
Orders, deliveries, invoices and payments, each posting to the ledger as it happens. Receivables aging and the open orders come from the same records.
- Invoices bill what was delivered
- Receivables aging by due date
- Cost of goods sold booked on delivery
Sample: a Claude Code session
Give your agent an ERP that refuses bad writes.
47 MCP tools for purchasing, sales, stock and the ledger. The rules live in the server, not in your prompt.
- Typed tools that resolve partners and items by name
- Refusals your agent can read and fix
- SQLite and one Python process, under Apache 2.0
Enterprise
Run it yourself, or let Attri run it.Either way, the records stay in your environment.
Self-hosted
Free and open source
Run OpenERP on your own machine and connect your agents to it today.
Hosted by you
- Full source code under Apache 2.0
- One SQLite file and one Python process
- Community support on GitHub
Managed by Attri
Built into your environment
The rules are open source. Attri runs OpenERP inside your infrastructure, next to the systems your operations team already uses.
In your environment, run by Attri
- Access control and approval rules for agent writes
- Connectors to the systems you already run
- Support from the team that builds OpenERP
Three-way match on every bill
Price against the purchase order, quantity against the goods received. A mismatch is refused.
Stock that can't go negative
A delivery or write-off larger than what's on hand is refused.
Balanced on write
Every document posts a journal entry whose debits equal its credits, in whole cents.
Audited in the same transaction
Each document and its audit row commit together, so the log can't fall behind.
Open source
Read the code. Run it today.Apache 2.0, running in minutes.
$ git clone https://github.com/Attri-Inc/open-erp.git
$ cd open-erp
$ python3 -m venv .venv && source .venv/bin/activate
$ pip install -e ".[dev]"
$ python scripts/seed.py
$ python run_mcp.py
# MCP server over stdio, sample business in data/openerp.db
$ docker compose up --build
# MCP over streamable HTTP on 127.0.0.1:8793, data in the openerp-data volume
$ claude mcp add openerp -s user -- $PWD/.venv/bin/python $PWD/run_mcp.py
# Run from the open-erp folder. 47 tools over stdio.
- 47MCP tools for Claude
- SQLiteOne file, one Python process
- Apache 2.0License
Seeds a small business, mid-cycle, with one command. Access control, approval rules and connectors to your systems come with an Attri deployment.
Read the README on GitHubOpen source by Attri
Part of Open Tooling.Standalone projects, all Apache 2.0.
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Purchasing, stock and sales your AI can't fudge. Bills must match; stock can't go below zero.
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- self-hosted
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Let your agents run purchasing and stock.Keep the rules on the server.
Run OpenERP on a sample business in minutes, or have Attri deploy it inside your environment with access control and approval rules.