Populate the store with a realistic demo dataset: 8 clients across 5 archetypes (on-time, late-payer, high-value, new, chronic-late) and 25-45 invoices spanning the last 6 months (paid, sent, and overdue). Every invoice has line items, tax, payment history, and reminder metadata. Use this to evaluate InvoiceFlow via MCP Inspector without real Stripe, SendGrid, or PayPal credentials — invoice_list, cashflow_report, invoice_risk, and payment_reconcile all return meaningful results against the returned ids. Safe to call multiple times; each call appends a fresh batch with unique UUIDs. Returns counts plus sample_invoice_ids you can feed straight into invoice_risk or invoice_mark_paid.

Create or upsert a client record used by invoice_create. Accepts name, email, company, address, city, country, tax_id, phone, default_currency ("USD"|"EUR"|"GBP"|...) and notes. Returns the stored client object including the generated id (UUID), an empty payment_history (populated as invoices are paid), and timestamps. Safe to call repeatedly: if a client with the same email already exists, the existing record is returned unchanged.

Create a new invoice for an existing client. Required: client_id (UUID) and line_items (non-empty array of {description, quantity, unit_price, tax_rate?, discount_percent?} — tax and discount are per-line). Optional: currency (defaults to the client's default_currency then USD), issue_date (YYYY-MM-DD or full ISO, defaults to today), due_date (same format, defaults to issue_date + 30 days), notes, and terms. Auto-calculates subtotal, discount_total, tax_total, and total; generates a sequential invoice_number in format INV-YYYY-NNNN; sets status="draft". Returns the full invoice object ready for invoice_send.

Search and filter invoices. Optional filters: status ("draft"|"sent"|"viewed"|"paid"|"overdue"|"cancelled"|"refunded"), client_id, min_amount, max_amount, date_from/date_to (ISO dates), overdue_only (boolean). Pagination via limit (default 50, max 200) and offset. Returns {total, invoices[]} where each invoice includes full line_items and payment state. Use this to build dashboards or drive invoice_remind/invoice_risk workflows.

Generate the invoice PDF and deliver it to the client. Always generates the PDF and marks the invoice status="sent". Email delivery via SendGrid is attempted automatically when the SENDGRID_API_KEY environment variable is set; without it the PDF is still generated and the status still advances so the caller can handle delivery out-of-band. Returns a confirmation message with the PDF size.

Record a full or partial payment against an invoice. Updates amount_paid and amount_due; sets status="paid" only when the outstanding balance reaches zero. As a side effect, a fully-paid invoice updates the client payment_history (total_revenue, paid_invoices, avg_days_to_payment, late_payment_count) which invoice_risk then uses for future predictions. Returns a confirmation with the paid amount and remaining balance.

Record that a payment reminder has been issued for an unpaid invoice. Increments reminder_count, sets last_reminder_at, and advances draft → sent. Returns the generated reminder message (custom or default) so the caller can relay it through their preferred channel — this tool itself does not send email; use invoice_send for actual delivery. Safely refuses to remind on already-paid invoices.

Predict late-payment risk for a specific invoice on a 0-100 scale. The model combines invoice amount (relative to client average), client payment history (avg_days_to_payment, late_payment_count), days remaining until due date, and prior reminder_count. Returns {risk_score (0-100), risk_level ("low"|"medium"|"high"|"critical"), factors (array of {factor, impact, detail}), recommended_action (string), next_reminder_date (ISO string or null)}. Use for prioritizing collection effort on high-value invoices.

Generate a portfolio-wide cash flow summary across all invoices. Returns {period, total_invoiced, total_collected, total_outstanding, total_overdue, collection_rate (percent), avg_days_to_payment (or null if no paid history), projected_income_30d (forecast based on due dates and historical pay rate), breakdown_by_status, breakdown_by_client}. Takes no input — always reports on the current full dataset. Ideal for dashboards and monthly close.

Match an incoming external payment (e.g. Stripe webhook, PayPal IPN, bank transfer) to an open invoice. Matching rule: the payer_email must equal the invoice client_email (case-insensitive) AND the payment_amount must equal the invoice amount_due within one cent. On match the invoice is marked paid, amount_paid/amount_due are updated, and client payment_history is recomputed exactly like invoice_mark_paid. Returns a reconciliation message on match or a "no match" message otherwise (no error). If multiple invoices match, the first one is reconciled.