Initial commit: Grist double-entry accounting skill

SKILL.md

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+---
+name: grist-accounting
+description: Use when working with the Grist double-entry accounting system - recording transactions, entering bills, tracking vendors, querying account balances, or generating financial reports
+---
+
+# Grist Double-Entry Accounting System
+
+## Overview
+
+A complete double-entry accounting system for sole proprietorship service businesses. Every transaction creates balanced journal entries (debits = credits). Account balances roll up through parent-child hierarchy.
+
+## Schema Quick Reference
+
+| Table | Purpose | Key Fields |
+|-------|---------|------------|
+| Accounts | Chart of accounts | Code, Name, Type, Parent, Balance |
+| Transactions | Journal entry headers | Date, Description, Reference, Status |
+| TransactionLines | Debits and credits | Transaction, Account, Debit, Credit |
+| Vendors | People you pay | Name, PaymentTerms, Balance |
+| Items | Common purchases | Name, DefaultAccount |
+| Bills | AP invoices | Vendor, BillDate, DueDate, Status, Amount, AmountDue |
+| BillLines | Bill line items | Bill, Item, Account, Amount |
+| BillPayments | Payment tracking | Bill, Transaction, Amount |
+| ReportingPeriods | Date ranges | Name, StartDate, EndDate, IsClosed |
+
+## Account Types
+
+| Type | Normal Balance | Examples |
+|------|----------------|----------|
+| Asset | Debit | Cash, AR, Prepaid |
+| Liability | Credit | AP, Credit Cards, Due to Owner |
+| Equity | Credit | Owner's Investment, Draws, Retained Earnings |
+| Income | Credit | Service Revenue, Interest Income |
+| Expense | Debit | Rent, Utilities, Office Supplies |
+
+## Common Workflows
+
+### Record a Simple Expense
+
+```python
+# Pay $50 for office supplies from checking
+transaction = add_records("Transactions", [{
+    "Date": "2026-01-03",
+    "Description": "Office supplies",
+    "Status": "Cleared"
+}])
+
+add_records("TransactionLines", [
+    {"Transaction": txn_id, "Account": office_supplies_id, "Debit": 50},
+    {"Transaction": txn_id, "Account": checking_id, "Credit": 50}
+])
+```
+
+### Enter a Bill (Accounts Payable)
+
+1. Create Bill record with Vendor, BillDate, DueDate
+2. Add BillLines with Item/Account and Amount
+3. Create Transaction: Debit expense accounts, Credit AP
+4. Link Bill.EntryTransaction to the transaction
+
+```python
+# $150 electric bill from vendor
+bill = add_records("Bills", [{
+    "Vendor": vendor_id,
+    "BillDate": "2026-01-03",
+    "DueDate": "2026-02-02",
+    "Status": "Open"
+}])
+
+add_records("BillLines", [{
+    "Bill": bill_id,
+    "Account": utilities_id,
+    "Description": "January electric",
+    "Amount": 150
+}])
+
+# Journal entry
+txn = add_records("Transactions", [{
+    "Date": "2026-01-03",
+    "Description": "Electric Co - January"
+}])
+
+add_records("TransactionLines", [
+    {"Transaction": txn_id, "Account": utilities_id, "Debit": 150},
+    {"Transaction": txn_id, "Account": ap_id, "Credit": 150}
+])
+
+# Link bill to transaction
+update_records("Bills", [{"id": bill_id, "fields": {"EntryTransaction": txn_id}}])
+```
+
+### Pay a Bill
+
+```python
+# Pay $150 bill
+txn = add_records("Transactions", [{
+    "Date": "2026-01-15",
+    "Description": "Payment - Electric Co",
+    "Reference": "Check #1001"
+}])
+
+add_records("TransactionLines", [
+    {"Transaction": txn_id, "Account": ap_id, "Debit": 150},
+    {"Transaction": txn_id, "Account": checking_id, "Credit": 150}
+])
+
+add_records("BillPayments", [{
+    "Bill": bill_id,
+    "Transaction": txn_id,
+    "Amount": 150,
+    "PaymentDate": "2026-01-15"
+}])
+
+# Bill.Status auto-updates based on AmountDue formula
+```
+
+### Owner Reimbursement
+
+When owner pays business expense personally:
+```python
+# Debit expense, Credit "Due to Owner" (liability 2203)
+add_records("TransactionLines", [
+    {"Transaction": txn_id, "Account": expense_id, "Debit": 50},
+    {"Transaction": txn_id, "Account": due_to_owner_id, "Credit": 50}
+])
+```
+
+When business reimburses owner:
+```python
+# Debit "Due to Owner", Credit Checking
+add_records("TransactionLines", [
+    {"Transaction": txn_id, "Account": due_to_owner_id, "Debit": 50},
+    {"Transaction": txn_id, "Account": checking_id, "Credit": 50}
+])
+```
+
+## Querying Data
+
+### Get Account Balances
+
+```python
+# All accounts with balances
+sql_query("SELECT Code, Name, Type, Balance FROM Accounts ORDER BY Code")
+
+# Cash accounts only
+sql_query("SELECT Name, Balance FROM Accounts WHERE Parent = 1")  # Parent 1 = Cash
+
+# Total by account type
+sql_query("SELECT Type, SUM(Balance) FROM Accounts WHERE Parent IS NULL GROUP BY Type")
+```
+
+### Get Unpaid Bills
+
+```python
+sql_query("""
+    SELECT v.Name, b.BillNumber, b.DueDate, b.AmountDue
+    FROM Bills b
+    JOIN Vendors v ON b.Vendor = v.id
+    WHERE b.Status IN ('Open', 'Partial')
+    ORDER BY b.DueDate
+""")
+```
+
+### Transaction History for Account
+
+```python
+sql_query("""
+    SELECT t.Date, t.Description, tl.Debit, tl.Credit
+    FROM TransactionLines tl
+    JOIN Transactions t ON tl.Transaction = t.id
+    WHERE tl.Account = ?
+    ORDER BY t.Date DESC
+""", account_id)
+```
+
+## Key Account Codes
+
+| Code | Name | Use For |
+|------|------|---------|
+| 1001 | Checking Account | Primary bank account |
+| 2000 | Accounts Payable | Bills owed to vendors |
+| 2203 | Due to Owner | Owner reimbursements |
+| 3002 | Owner's Draws | Money withdrawn by owner |
+| 4001 | Service Revenue | Primary income |
+
+## Validation Rules
+
+1. **Transactions must balance**: `SUM(Debit) = SUM(Credit)`
+2. **Each line has Debit OR Credit**, not both
+3. **Bills need at least one BillLine**
+4. **BillPayments cannot exceed AmountDue**
+
+## Formula Columns (Auto-Calculated)
+
+| Table.Column | Formula |
+|--------------|---------|
+| Accounts.Balance | OwnBalance + ChildrenBalance |
+| Transactions.IsBalanced | Sum debits = Sum credits |
+| Bills.Amount | Sum of BillLines.Amount |
+| Bills.AmountDue | Amount - AmountPaid |
+| Vendors.Balance | Sum of unpaid bills |
+
+## Common Mistakes
+
+| Mistake | Fix |
+|---------|-----|
+| Transaction not balanced | Ensure debits = credits before saving |
+| Wrong debit/credit direction | Assets/Expenses increase with debit; Liabilities/Equity/Income increase with credit |
+| Posting to parent account | Post to leaf accounts (1001 Checking, not 1000 Cash) |
+| Forgetting AP entry for bills | Bills need both the expense entry AND the AP credit |