OpenAIとGoogleテーブルを使ったPDF請求書処理と承認プロセスの自動化

• •Googleアカウント + Gmail API認証情報
• •Google Drive API認証情報
• •Google Sheets API認証情報
• •OpenAI API Key

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  "nodes": [
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      "parameters": {
        "model": {
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          "mode": "list",
          "value": "gpt-4o-mini"
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      "type": "@n8n/n8n-nodes-langchain.outputParserStructured",
      "position": [
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      "parameters": {
        "jsonSchemaExample": "{\n  \"invoice_number\": \"\",\n  \"invoice_date\": \"\",\n  \"due_date\": \"\",\n  \"vendor_name\": \"\",\n  \"total_amount\": \"\",\n  \"currency\": \"\",\n  \"items\": [\n    {\n      \"description\": \"\",\n      \"amount\": \"\"\n    }\n  ],\n  \"tax\": \"\",\n  \"category\": \"\"\n}"
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      "id": "b7ed6cf6-e965-43e0-abab-919ab598e62a",
      "name": "Invoice Folder Monitor",
      "type": "n8n-nodes-base.googleDriveTrigger",
      "position": [
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      "parameters": {
        "event": "fileCreated",
        "options": {},
        "pollTimes": {
          "item": [
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        "triggerOn": "specificFolder",
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      "position": [
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        "fileId": {
          "__rl": true,
          "mode": "id",
          "value": "={{ $json.id }}"
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        "operation": "download"
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      "type": "@n8n/n8n-nodes-langchain.agent",
      "position": [
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      "parameters": {
        "text": "=You are an intelligent invoice parser. I will give you raw text extracted from a PDF invoice. \n\n========================\nSTART OF RAW INVOICE TEXT\n\n{{ $json.text }}\n\nEND OF RAW INVOICE TEXT\n========================\n\nYour job is to:\n\n1. Extract key information from the invoice such as:\n   - invoice_number\n   - invoice_date\n   - due_date (if available)\n   - vendor_name\n   - total_amount\n   - currency (e.g., USD, IDR, etc.)\n   - items (as a list of item descriptions and their amounts)\n   - tax (if available)\n\n2. Detect the invoice **category**, such as:\n   - Utilities\n   - Office Supplies\n   - Travel\n   - Software\n   - Food & Beverage\n   - Others (if unknown)\n\n3. Return the result in this exact JSON format:\n\n```json\n{\n  \"invoice_number\": \"\",\n  \"invoice_date\": \"\",\n  \"due_date\": \"\",\n  \"vendor_name\": \"\",\n  \"total_amount\": \"\",\n  \"currency\": \"\",\n  \"items\": [\n    {\n      \"description\": \"\",\n      \"amount\": \"\"\n    }\n  ],\n  \"tax\": \"\",\n  \"category\": \"\"\n}\n",
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      "id": "57649f6a-2d4d-4072-92bd-ffea26fdd4dd",
      "name": "Insert Invoice Data",
      "type": "n8n-nodes-base.googleSheets",
      "position": [
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      "parameters": {
        "columns": {
          "value": {
            "Tax": "={{ $('Invoice Parser AI Agent').item.json.output.tax }}",
            "Items": "={{ $('Invoice Parser AI Agent').item.json.output.items }}",
            "Approved": "={{ $json.data['Approve Invoice?'] }}",
            "Category": "={{ $('Invoice Parser AI Agent').item.json.output.category }}",
            "Currency": "={{ $('Invoice Parser AI Agent').item.json.output.currency }}",
            "Due Date": "={{ $('Invoice Parser AI Agent').item.json.output.due_date }}",
            "Reviewed By": "={{ $json.data['Reviewed By'] }}",
            "Vendor Name": "={{ $('Invoice Parser AI Agent').item.json.output.vendor_name }}",
            "Invoice Date": "={{ $('Invoice Parser AI Agent').item.json.output.invoice_date }}",
            "Total Amount": "={{ $('Invoice Parser AI Agent').item.json.output.total_amount }}",
            "Approval Notes": "={{ $json.data['Approval Notes'] }}",
            "Invoice Number": "={{ $('Invoice Parser AI Agent').item.json.output.invoice_number }}"
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              "id": "Invoice Number",
              "type": "string",
              "display": true,
              "required": false,
              "displayName": "Invoice Number",
              "defaultMatch": false,
              "canBeUsedToMatch": true
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              "id": "Invoice Date",
              "type": "string",
              "display": true,
              "required": false,
              "displayName": "Invoice Date",
              "defaultMatch": false,
              "canBeUsedToMatch": true
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              "type": "string",
              "display": true,
              "required": false,
              "displayName": "Due Date",
              "defaultMatch": false,
              "canBeUsedToMatch": true
            },
            {
              "id": "Vendor Name",
              "type": "string",
              "display": true,
              "required": false,
              "displayName": "Vendor Name",
              "defaultMatch": false,
              "canBeUsedToMatch": true
            },
            {
              "id": "Total Amount",
              "type": "string",
              "display": true,
              "required": false,
              "displayName": "Total Amount",
              "defaultMatch": false,
              "canBeUsedToMatch": true
            },
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              "type": "string",
              "display": true,
              "required": false,
              "displayName": "Currency",
              "defaultMatch": false,
              "canBeUsedToMatch": true
            },
            {
              "id": "Items",
              "type": "string",
              "display": true,
              "required": false,
              "displayName": "Items",
              "defaultMatch": false,
              "canBeUsedToMatch": true
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            {
              "id": "Tax",
              "type": "string",
              "display": true,
              "required": false,
              "displayName": "Tax",
              "defaultMatch": false,
              "canBeUsedToMatch": true
            },
            {
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              "type": "string",
              "display": true,
              "required": false,
              "displayName": "Category",
              "defaultMatch": false,
              "canBeUsedToMatch": true
            },
            {
              "id": "Approved",
              "type": "string",
              "display": true,
              "required": false,
              "displayName": "Approved",
              "defaultMatch": false,
              "canBeUsedToMatch": true
            },
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              "display": true,
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              "displayName": "Approval Notes",
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          "cachedResultName": "Invoices"
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          "name": "Google Sheets account"
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      "position": [
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      "parameters": {
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        "width": 280,
        "height": 500,
        "content": "## SETUP REQUIRED\n\nGoogle Sheets Structure:\nSheet: \"Invoices\"\n• Column A: Invoice Number  \n• Column B: Invoice Date  \n• Column C: Due Date  \n• Column D: Vendor Name  \n• Column E: Total Amount  \n• Column F: Currency  \n• Column G: Items  \n• Column H: Tax  \n• Column I: Category  \n• Column J: Approved\n• Column K: Approval Notes\n• Column L: Reviewed By\n\nRequired Credentials:\n• Google Drive Credential  \n• Gmail Credential \n• Google Sheets Credential \n• OpenAI API Key (GPT-4)\n"
      },
      "typeVersion": 1
    },
    {
      "id": "691f4972-8d18-49fd-b8cd-0c6b2464b078",
      "name": "付箋3",
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      "parameters": {
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        "width": 700,
        "height": 560,
        "content": "## 🧾 Automated PDF Invoice Processing & Approval Flow using OpenAI and Google Sheets\n\nWhat This Template Does:\n\n- Monitors **Google Drive**, **Gmail**, and a **web form** for incoming PDF invoices  \n- Automatically downloads and extracts raw text from PDF attachments  \n- Uses **GPT-4o-mini** to intelligently parse invoice data (invoice number, vendor, date, amount, tax, items, etc.)  \n- Categorizes invoices into types such as *Utilities, Travel, Office Supplies, Food & Beverage, Others*  \n- Sends a dynamic **approval request email** with an embedded decision form (Yes/No, reviewer name, notes)  \n- Stores both approved and rejected invoice data into **Google Sheets** for recordkeeping  \n- Sends rejection notifications to the finance team for follow-up  \n- Provides a complete, automated approval pipeline with human oversight  \n- Includes a structured JSON schema for consistent and error-free AI output  \n- Polls input sources every minute to ensure timely and responsive processing  \n- Ideal for businesses seeking to **automate their invoice approval and bookkeeping workflows** with AI\n\n"
      },
      "typeVersion": 1
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    {
      "id": "2463666d-8c40-4821-b907-9741e62ce1e7",
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      "position": [
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      "parameters": {
        "color": 5,
        "width": 620,
        "height": 620,
        "content": "## 📋 WORKFLOW PROCESS OVERVIEW\n\n1. **Invoice Collection**  \nInvoices are captured through three triggers: new PDFs in a Google Drive folder, incoming Gmail messages with PDF attachments, or direct uploads via a web form.\n\n2. **File Handling**  \nIf uploaded via Drive, the PDF is downloaded using its file ID; if via Gmail or form, the PDF is already available as binary data.\n\n3. **Text Extraction**  \nThe system extracts raw text from the PDF using the appropriate method based on its source (Drive, Email, or Form).\n\n4. **AI Data Parsing**  \nGPT-4 processes the extracted text into structured JSON, identifying invoice details like vendor, date, amount, and categorizing the invoice.\n\n5. **Approval Request**  \nAn email is sent to the reviewer with an approval form asking for a Yes/No decision along with optional notes.\n\n6. **Decision Routing**  \nIf approved, the data moves forward for storage; if rejected, a notification is sent to the finance team.\n\n7. **Save Invoice Data**  \nAll extracted and reviewed invoice data is saved into a Google Sheet, maintaining a full record of each invoice and its status.\n"
      },
      "typeVersion": 1
    },
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      "name": "Send Invoice for Approval",
      "type": "n8n-nodes-base.gmail",
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      "webhookId": "a23938a4-fc6c-4445-8dee-17e501e92e06",
      "parameters": {
        "sendTo": "replace_with_approver_email@yopmail.com",
        "message": "=A new invoice has been submitted and requires your review and approval:",
        "options": {},
        "subject": "=[Action Required] Invoice Approval Request – {{ $json.output.vendor_name }}",
        "operation": "sendAndWait",
        "formFields": {
          "values": [
            {
              "fieldType": "dropdown",
              "fieldLabel": "Approve Invoice?",
              "fieldOptions": {
                "values": [
                  {
                    "option": "Yes"
                  },
                  {
                    "option": "No"
                  }
                ]
              },
              "requiredField": true
            },
            {
              "fieldLabel": "Reviewed By",
              "requiredField": true
            },
            {
              "fieldType": "textarea",
              "fieldLabel": "Approval Notes"
            }
          ]
        },
        "responseType": "customForm"
      },
      "credentials": {
        "gmailOAuth2": {
          "id": "sWl7FFMkEUYBj0zM",
          "name": "Gmail account"
        }
      },
      "typeVersion": 2.1
    },
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      "name": "Monitor メール Attachments",
      "type": "n8n-nodes-base.gmailTrigger",
      "position": [
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        "simple": false,
        "filters": {},
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          "downloadAttachments": true,
          "dataPropertyAttachmentsPrefixName": "attachment_"
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              "fieldLabel": "Upload",
              "multipleFiles": false,
              "requiredField": true,
              "acceptFileTypes": ".pdf"
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        "formDescription": "Upload your invoice PDF using this form."
      },
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        "operation": "pdf",
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      "parameters": {
        "sendTo": "finance_team@yopmail.com",
        "message": "=Hi Finance Team,\n\nAn invoice from {{ $('Invoice Parser AI Agent').item.json.output.vendor_name }} has been disapproved during the approval process.\n\nReviewed By: {{ $('Send Invoice for Approval').item.json.data['Reviewed By'] }}\nApproval Notes: {{ $('Send Invoice for Approval').item.json.data['Approval Notes'] }}\n\nPlease review and follow up as needed.\n\nThank you,\nAutomated Invoice System\n\n",
        "options": {
          "appendAttribution": false
        },
        "subject": "=[Alert] Invoice Disapproved – {{ $('Invoice Parser AI Agent').item.json.output.vendor_name }}",
        "emailType": "text"
      },
      "credentials": {
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        }
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    }
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      {
        "output": {
          "tax": "8.50",
          "items": [
            {
              "amount": "85.00",
              "description": "Web Design - This is a sample description..."
            }
          ],
          "category": "Others",
          "currency": "USD",
          "due_date": "January 31, 2016",
          "vendor_name": "DEMO - Sliced Invoices",
          "invoice_date": "January 25, 2016",
          "total_amount": "93.50",
          "invoice_number": "INV-3337"
        }
      }
    ],
    "Send Invoice for Approval": [
      {
        "data": {
          "Reviewed By": "jack",
          "Approval Notes": "notes approval",
          "Approve Invoice?": "Yes"
        }
      }
    ]
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  "connections": {
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