MCP Universal EC E-Invoice Server

繁體中文

An open-source MCP (Model Context Protocol) server wrapping the Universal EC (汎宇電商) Taiwan E-Invoice POS Web Service (JSON format, MIG4.1). Exposes 27 AI-callable tools covering all available function codes via stdio JSON-RPC 2.0.

Built for Claude Code and any MCP-compatible AI client. Enables AI agents to issue invoices, void invoices, manage invoice numbers, query cancellation status, and handle allowances through natural language.

Features

• 27 MCP tools — Full coverage of all Universal EC e-invoice API function codes
• stdio JSON-RPC 2.0 — Standard MCP transport protocol
• 3 wrapper formats — INDEX, Invoice, Allowance (auto-selected per function)
• Credential injection — SELLERID/POSID/POSSN auto-injected by connector
• TDD tested — 53 unit tests + 5 live regression tests

Quick Start

# Setup
uv venv && source .venv/bin/activate
uv pip install -e ".[dev]"

# Configure credentials
cp .env.example .env
# Edit .env with your Universal EC credentials

# Run server
python mcp_server.py

Configuration

Create a .env file with your Universal EC POS credentials:

EINVOICE_BASE_URL=https://epostw.einvoice.com.tw/GetInvoice.ashx
EINVOICE_SELLER_ID=your_seller_id
EINVOICE_POS_ID=your_pos_id
EINVOICE_POS_SN=your_pos_sn

Environment	URL
Test (測試機)	https://epostw.einvoice.com.tw/GetInvoice.ashx
Production (正式機)	https://eposw.einvoice.com.tw/GetInvoice.ashx

Project Structure

mcp-universalec-e-invoice/
├── app.py                          # FastMCP singleton
├── mcp_server.py                   # Entry point (stdio transport)
├── config/
│   └── settings.py                 # URL + credentials from .env
├── connectors/
│   └── einvoice_client.py          # Single POST connector (3 wrappers)
├── tools/
│   ├── system_tools.py             # Y01
│   ├── invoice_number_tools.py     # A01, C01, Z21, Z22
│   ├── b2c_invoice_tools.py        # C0401, C0401N, C0501
│   ├── b2b_invoice_tools.py        # A0401, A0501, A0101, A0201
│   ├── allowance_tools.py          # D0401, D0401N, D0501, B0401, B0501, B0101
│   ├── cancel_tools.py             # C0701, B0701
│   ├── query_tools.py              # Z11, Z31, Z33, Z34
│   └── admin_tools.py              # Z32, E0401, E0402
└── tests/
    ├── conftest.py                 # Shared fixtures
    ├── test_einvoice_client.py     # Connector unit tests
    ├── test_system_tools.py        # Y01 tests
    ├── test_invoice_number_tools.py
    ├── test_b2c_invoice_tools.py
    ├── test_b2b_invoice_tools.py
    ├── test_allowance_tools.py
    ├── test_cancel_tools.py
    ├── test_query_tools.py
    ├── test_admin_tools.py
    └── test_regression.py          # Live API tests

Tools (27 total)

System

Tool	Code	Description
get_system_time	Y01	Connection test / get server time

Invoice Number Management

Tool	Code	Description
get_invoice_numbers	A01	Get invoice number allocation (current period)
get_next_period_numbers	C01	Get invoice number allocation (next period)
get_invoice_numbers_expanded	Z21	Get numbers expanded per-invoice with AESKEY
get_next_period_numbers_expanded	Z22	Get next period numbers expanded with AESKEY

B2C Invoices

Tool	Code	Description
create_b2c_invoice	C0401	Create B2C invoice (positional field format)
create_b2c_invoice_named	C0401N	Create B2C invoice (named field format)
void_b2c_invoice	C0501	Void a B2C invoice

B2B Invoices

Tool	Code	Description
create_b2b_invoice	A0401	Create B2B invoice (platform certified)
void_b2b_invoice	A0501	Void a B2B invoice
create_b2b_exchange_invoice	A0101	Create B2B exchange invoice
void_b2b_exchange_invoice	A0201	Void a B2B exchange invoice

Allowances (折讓)

Tool	Code	Description
create_b2c_allowance	D0401	Create B2C allowance
create_b2c_allowance_named	D0401N	Create B2C allowance (named format)
void_b2c_allowance	D0501	Void a B2C allowance
create_b2b_allowance	B0401	Create B2B allowance
void_b2b_allowance	B0501	Void a B2B allowance
create_b2b_exchange_allowance	B0101	Create B2B exchange allowance

Cancellation (註銷)

Tool	Code	Description
cancel_invoice	C0701	Cancel an invoice
batch_cancel_invoice	B0701	Batch cancel with full invoice data

Queries

Tool	Code	Description
get_cancel_status	Z11	Get invoice cancel process status
get_downloaded_track_ranges	Z31	Query downloaded track ranges
get_assignment_info	Z33	Query tax ID number assignment
get_winning_list	Z34	Download winning invoice list

Administration

Tool	Code	Description
upload_next_period_tracks	Z32	Upload next period track numbers
assign_branch_tracks	E0401	Branch office track assignment
report_unused_tracks	E0402	Report unused track ranges

Usage Examples

Once the MCP server is running, an AI assistant (e.g. Claude) can call these tools on your behalf. Here are real-world scenarios showing what you say and how the AI responds.

---

"Help me check if the e-invoice system is connected"

You: 幫我測試一下電子發票系統有沒有連線成功

AI calls: get_system_time()

Result: The system returns REPLY: "1" with MESSAGE: "連線成功" and the server time 2026/04/01 22:29:03. Your connection is working.

---

"What invoice numbers do I have available right now?"

You: 我目前有哪些可用的發票號碼？

AI calls: get_invoice_numbers()

Result: Current period is 115 年 03-04 月, track GS, numbers 82775400 ~ 82775449 (50 invoices available). The AI can also explain the QRCode AES key returned for barcode generation.

---

"I need to get the detailed invoice numbers with AES keys for printing"

You: 我需要取得每張發票的 AESKEY 跟隨機碼，準備列印用

AI calls: get_invoice_numbers_expanded()

Result: Returns 50 individual invoices, each with its own number, AESKEY, and random number:

GS82775450 → AESKEY: Xymp9aqy..., RandomNumber: 7833
GS82775451 → AESKEY: XausdWBO..., RandomNumber: 4581
...

---

"Issue an invoice for a customer who bought 2 lattes and 1 cake"

You: 幫我開一張發票，客人買了 2 杯拿鐵 65 元、1 個巧克力蛋糕 85 元，總共 215 元含稅，紙本發票已列印

AI calls: get_invoice_numbers_expanded() to get an available number, then:

create_b2c_invoice(
  invoice_number = "GS82775402",     ← from the allocation
  invoice_date   = "2026-04-01",
  invoice_time   = "14:30:00",
  buyer_id       = "0000000000",     ← consumer, no tax ID
  buyer_name     = "0000",
  invoice_type   = "07",
  donate_mark    = "0",
  print_mark     = "Y",
  random_number  = "6136",           ← from the allocation
  tax_type = "1", tax_rate = "0.05", tax_amount = "10",
  sales_amount = "205", free_tax = "0", zero_tax = "0", total = "215",
  items = [
    {B1:"1", B2:"拿鐵咖啡", B3:"2", B5:"65", B6:"130", B7:"1", B13:"1"},
    {B1:"2", B2:"巧克力蛋糕", B3:"1", B5:"85", B6:"85", B7:"2", B13:"1"},
  ]
)

Result: REPLY: "1", MESSAGE: "成功", invoice GS82775402 created.

---

"Please void invoice GS82775401"

You: 請幫我作廢發票 GS82775401，原因是客戶取消訂單

AI calls:

void_b2c_invoice(
  invoice_number = "GS82775401",
  invoice_date   = "2026-04-01",
  buyer_id       = "0000000000",
  seller_id      = "23997652",
  cancel_date    = "2026-04-01",
  cancel_time    = "15:00:00",
  cancel_reason  = "客戶取消訂單",
)

Result: REPLY: "1", MESSAGE: "成功" — invoice voided successfully.

---

"Check the cancellation status of invoice GS82775400"

You: 幫我查一下 GS82775400 這張發票的註銷狀態

AI calls: get_cancel_status(invoice_number="GS82775400", invoice_date="2026-04-01")

Result: STATUSCODE: "1" = completed, "2" = pending, "3" = failed. The AI interprets and tells you the current status in plain language.

---

"Cancel invoice GS82775400 — it was issued by mistake"

You: 發票 GS82775400 開錯了，幫我註銷

AI calls:

cancel_invoice(
  invoice_number = "GS82775400",
  invoice_date   = "2026-04-01",
  buyer_id       = "0000000000",
  seller_id      = "23997652",
  cancel_date    = "2026-04-01",
  cancel_time    = "16:00:00",
  cancel_reason  = "誤開發票",
)

Result: If the invoice has been uploaded to the tax authority, REPLY: "1" confirms cancellation. If it hasn't been uploaded yet, the system returns REPLY: "-1" with a message explaining the invoice is still being processed — the AI will tell you to try again later.

Note: "作廢" (C0501 void) and "註銷" (C0701 cancel) are different. Void happens before upload to tax authority; cancel happens after. The AI picks the right tool based on context.

---

"I need to check what invoice number ranges have been downloaded"

You: 查一下統編 23997652 在 11504 期的 GS 字軌已下載的配號區間

AI calls:

get_downloaded_track_ranges(
  head_ban      = "23997652",
  branch_ban    = "23997652",
  invoice_type  = "07",
  year_month    = "11504",
  invoice_track = "GS",
)

Result: Returns the track ranges that have been successfully downloaded for this period.

Testing

# Unit tests (mocked HTTP, no credentials needed)
pytest tests/ --ignore=tests/test_regression.py -v

# Regression tests (requires .env with valid credentials)
pytest tests/test_regression.py -v -s

Architecture

All 27 functions communicate through a single POST endpoint (GetInvoice.ashx), differentiated by function code in the JSON body. The connector auto-injects credentials (SELLERID, POSID, POSSN) and system time.

Three JSON wrapper formats:

• INDEX — System/number functions (Y01, A01, C01, Z21, Z22, Z11)
• Invoice — Invoice/allowance/admin CRUD (C0401, A0401, D0401, C0701, E0401, Z31, etc.)
• Allowance — B0501 only (void B2B allowance)

License

MIT License — see LICENSE for details.

Part of the Asgard Ecosystem

See the full Asgard AI Platform for more MCP servers.