🚀 Apps Script + Gemini Mastery — Issue #1

“Your First AI-Powered Script: Build a Smart Document Analyzer”

A newsletter series for experienced Google Apps Script developers who want to level up with AI-powered automation, real-world exercises, and fully working code.

⭐ Welcome to the Series

This series will teach you how to:

Use Gemini inside Apps Script
Build AI-powered tools (text analysis, data transformation, doc generation, automation)
Add custom UIs and integrate Gemini into Docs, Sheets, Slides & Gmail
Create deployable add-ons
Learn through hands-on exercises, full code, and clear setup steps

Each issue includes:

✔ A complete lesson
✔ A real project
✔ Full Apps Script source code
✔ A downloadable menu/UI
✔ Testing instructions
✔ “What you learned” section

📘 Lesson 1 — Build an AI Document Analyzer for Google Docs

This lesson teaches you how to build your first Gemini-powered automation:

Select text → Run “Analyze Text with Gemini” → Receive insights, summary, rewrite suggestions, sentiment analysis, and more.

Perfect for Docs users—and a strong start to the series.

🧠 What You Will Build

A custom Apps Script menu:

AI Tools
   → Analyze Selected Text
   → Summarize the Document
   → Rewrite for Clarity

Each option sends your text to Gemini and displays structured results in a sidebar.

🛠️ What You Will Learn

By the end of Issue #1, you’ll know how to:

Connect to the Gemini API through Apps Script
Create a custom menu (with submenus)
Build a sidebar UI
Extract selected text from Google Docs
Send requests to Gemini and handle responses
Output results cleanly back into the Doc

This is foundational for more advanced lessons (RAG, embeddings, agents, Sheets automation, Gmail AI tools, etc.)

🧩 EXERCISE — Build the AI Document Analyzer

STEP 1 — Set up the Script

Open any Google Doc → Extensions → Apps Script → Paste this code:

📄 Code: DocsMenu.gs

function onOpen() {
  DocumentApp.getUi()
    .createMenu("AI Tools")
    .addItem("Analyze Selected Text", "showAnalyzeSidebar")
    .addItem("Summarize Document", "summarizeDocument")
    .addItem("Rewrite for Clarity", "rewriteForClarity")
    .addToUi();
}

STEP 2 — Add Gemini Helper

Replace "YOUR_API_KEY" with your Gemini API Key:

📄 Code: GeminiHelpers.gs

const GEMINI_API_KEY = "YOUR_API_KEY";
const GEMINI_MODEL= 'gemini-2.0-flash';

function callGemini(prompt, text) {
  const url = `https://generativelanguage.googleapis.com/v1beta/models/${GEMINI_MODEL}:generateContent?key=${GEMINI_API_KEY}`;

  const payload = {
    contents: [{
      parts: [{
        text: `${prompt}\n\n---\n\n${text}`
      }]
    }]
  };

  const res = UrlFetchApp.fetch(url, {
    method: "post",
    contentType: "application/json",
    payload: JSON.stringify(payload),
    muteHttpExceptions: true
  });

  const json = JSON.parse(res.getContentText());

  return json.candidates?.[0]?.content?.parts?.[0]?.text || "No response from Gemini.";
}

STEP 3 — Build the Sidebar UI

📄 Code: Sidemenu.gs

function showAnalyzeSidebar() {
  const html = HtmlService.createHtmlOutputFromFile("Sidebar")
    .setTitle("AI Text Analyzer");
  DocumentApp.getUi().showSidebar(html);
}

function analyzeSelectedText() {
  const doc = DocumentApp.getActiveDocument();
  const selection = doc.getSelection();

  if (!selection) return "No text selected.";

  let text = "";

  selection.getRangeElements().forEach(el => {
    if (el.getElement().editAsText) {
      text += el.getElement().asText().getText() + "\n";
    }
  });

  const prompt = `
Analyze the following text. Provide:

1. Key insights  
2. Summary (3–5 bullet points)  
3. Suggested improvements  
4. Overall sentiment  
5. Rewrite for clarity  
`;

  return callGemini(prompt, text);
}

function summarizeDocument() {
  const bodyText = DocumentApp.getActiveDocument().getBody().getText();
  return callGemini("Summarize the following document:", bodyText);
}

function rewriteForClarity() {
  const bodyText = DocumentApp.getActiveDocument().getBody().getText();
  return callGemini("Rewrite the document for clarity and simplicity:", bodyText);
}

STEP 4 — Create the Sidebar HTML

📄 File: Sidebar.html

<div style="font-family: Arial; padding: 10px;">
  <h2>AI Document Analyzer</h2>

  <button onclick="run('analyzeSelectedText')">Analyze Selected Text</button>
  <button onclick="run('summarizeDocument')">Summarize Document</button>
  <button onclick="run('rewriteForClarity')">Rewrite for Clarity</button>

  <pre id="output" style="white-space: pre-wrap; margin-top: 20px;"></pre>

  <script>
    function run(fn) {
      google.script.run.withSuccessHandler(function(result) {
        document.getElementById("output").textContent = result;
      })[fn]();
    }
  </script>
</div>

🧪 Testing Instructions

Open a Google Doc
Highlight any text
Go to AI Tools → Analyze Selected Text
Watch results appear in the sidebar
Try the other menu items

If everything works, congratulations — you’ve built your first Gemini-powered Google Doc add-on!

🎓 What You Learned

Creating custom UI menus
Adding a sidebar
Extracting text
Structuring Gemini prompts
Handling API responses
Building reusable AI helpers

This foundation will support all advanced lessons to come:

Coming next in Issue #2:

🔥 AI-Powered Content Generator for Docs
Generate blog posts, lesson plans, and formatted documents using structured prompts + Gemini.

Here’s a setup Apps Script that will create the lesson content + sample text directly in the current Google Doc.

1. Add this function to your Apps Script project

Create a new file (e.g. SetupLessonDoc.gs) and paste:

function setupLessonDoc() {
  const doc = DocumentApp.getActiveDocument();
  const body = doc.getBody();

  // Start with a clean slate
  body.clear();

  // Title
  body.appendParagraph("Apps Script + Gemini Mastery — Issue #1")
      .setHeading(DocumentApp.ParagraphHeading.HEADING1);

  body.appendParagraph("Your First AI-Powered Script: Build a Smart Document Analyzer")
      .setHeading(DocumentApp.ParagraphHeading.HEADING2);

  body.appendParagraph(
    "This document was generated by the setup script. " +
    "Use it as your working file to test the AI Tools menu connected to Gemini."
  );

  body.appendParagraph("");

  // Section: What You Will Build
  body.appendParagraph("What You Will Build")
      .setHeading(DocumentApp.ParagraphHeading.HEADING2);

  body.appendParagraph(
    "In this lesson, you will build an AI-powered Document Analyzer for Google Docs. " +
    "You will be able to select text and then run AI Tools → Analyze Selected Text " +
    "to get insights, summaries, and rewrite suggestions from Gemini."
  );

  // Section: Instructions
  body.appendParagraph("How to Use This Doc with the AI Tools Menu")
      .setHeading(DocumentApp.ParagraphHeading.HEADING2);

  body.appendListItem("Select any paragraph or section of text below.")
      .setGlyphType(DocumentApp.GlyphType.BULLET);
  body.appendListItem("Open the menu: AI Tools → Analyze Selected Text.")
      .setGlyphType(DocumentApp.GlyphType.BULLET);
  body.appendListItem("Review the output in the sidebar (insights, summary, rewrite).")
      .setGlyphType(DocumentApp.GlyphType.BULLET);
  body.appendListItem("Experiment with Summarize Document and Rewrite for Clarity.")
      .setGlyphType(DocumentApp.GlyphType.BULLET);

  body.appendParagraph("");

  // Section: Sample Content to Analyze
  body.appendParagraph("Sample Article for AI Analysis")
      .setHeading(DocumentApp.ParagraphHeading.HEADING2);

  const sampleParagraphs = [
    "Most teams struggle to turn raw information into clear, usable knowledge. " +
      "Documents grow longer, feedback gets buried in email threads, and important " +
      "decisions are scattered across chats and comments.",

    "AI-powered tools like Gemini can help by quickly summarizing long documents, " +
      "highlighting key decisions, and suggesting better ways to express ideas. " +
      "Instead of manually rewriting paragraphs, you can focus on thinking and " +
      "strategy while the AI handles structure and phrasing.",

    "However, AI only becomes truly powerful when it is integrated into your existing workflow. " +
      "That is why Google Apps Script is such a valuable layer: it lets you bring Gemini " +
      "directly into Docs, Sheets, Slides, and Gmail, automating the tasks you already do " +
      "every day.",

    "In this lesson, you will experiment with an AI Document Analyzer that you can customize. " +
      "Try selecting different sections of this article and see how the AI changes its " +
      "summary, insights, and suggestions based on what you highlight."
  ];

  sampleParagraphs.forEach(text => body.appendParagraph(text));

  body.appendParagraph("");

  // Extra block of text for testing summaries
  body.appendParagraph("Longer Sample Section")
      .setHeading(DocumentApp.ParagraphHeading.HEADING3);

  body.appendParagraph(
    "Imagine you are responsible for reviewing weekly project reports from multiple " +
    "teams. Each report is several pages long, combining metrics, narrative updates, " +
    "risks, and next steps. Reading every word is unrealistic, but skipping sections " +
    "means missing important context. With an embedded AI assistant, you can highlight " +
    "a section and instantly ask for a concise summary, a list of risks, or a clearer " +
    "rewrite that you can paste into your own executive update."
  );

  body.appendParagraph(
    "This is the type of workflow enhancement that Apps Script + Gemini makes possible. " +
    "As you test the AI Tools menu on this document, think about the documents you " +
    "work with every day: course outlines, project charters, meeting notes, or client " +
    "proposals. Any place where you read, summarize, and rewrite text is an opportunity " +
    "to add intelligence with just a few lines of code."
  );

  body.appendParagraph("");
  body.appendParagraph("✅ Setup complete. You can now experiment with the AI Tools menu on this content.");
}

2. (Optional) Add a menu item to run the setup from Docs

If you want this available as a one-click option in the Doc UI, update your existing onOpen() like this:

function onOpen() {
  DocumentApp.getUi()
    .createMenu("AI Tools")
    .addItem("Analyze Selected Text", "showAnalyzeSidebar")
    .addItem("Summarize Document", "summarizeDocument")
    .addItem("Rewrite for Clarity", "rewriteForClarity")
    .addSeparator()
    .addItem("Setup Lesson Doc", "setupLessonDoc")
    .addToUi();
}

3. How to use it

Open your target Google Doc.
In Apps Script, run setupLessonDoc once (or use the menu item if you added it).
The document will be populated with:
- Title + subtitle for Issue #1
- Short explanation of the tool
- Instructions for using the AI menu
- Several paragraphs of realistic sample content to analyze

Then just use your Gemini-powered AI Tools menu on the generated text.