diff --git a/package.json b/package.json
index 286cddb..57570f1 100644
--- a/package.json
+++ b/package.json
@@ -7,7 +7,8 @@
     "packages/br-cal",
     "packages/br-script",
     "packages/discover-dl",
-    "packages/lm-sync"
+    "packages/lm-sync",
+    "packages/makesheet"
   ],
   "devDependencies": {
     "@endo/eslint-plugin": "^0.5.1",
diff --git a/packages/makesheet/.claspignore b/packages/makesheet/.claspignore
new file mode 100644
index 0000000..c1278dd
--- /dev/null
+++ b/packages/makesheet/.claspignore
@@ -0,0 +1,2 @@
+.git/**
+node_modules/**
diff --git a/packages/makesheet/.eslintrc.json b/packages/makesheet/.eslintrc.json
new file mode 100644
index 0000000..cec9acb
--- /dev/null
+++ b/packages/makesheet/.eslintrc.json
@@ -0,0 +1,37 @@
+{
+  "extends": [
+    "airbnb-base"
+  ],
+  "env": {
+    "es6": true
+  },
+  "rules": {
+    "quotes": [
+      "error",
+      "single",
+      {
+        "avoidEscape": true,
+        "allowTemplateLiterals": true
+      }
+    ],
+    "comma-dangle": ["error", "always-multiline"],
+    "no-console": "off",
+    "no-unused-vars": [
+      "error",
+      {
+        "argsIgnorePattern": "^_",
+        "varsIgnorePattern": "^_"
+      }
+    ],
+    "no-undef": "off",
+    "no-underscore-dangle": [
+      "error",
+      {
+        "allowAfterThis": false,
+        "allowAfterSuper": false,
+        "enforceInMethodNames": false,
+        "allow": ["_testDoGet", "_testCreateJsonResponse"]
+      }
+    ]
+  }
+}
diff --git a/packages/makesheet/.gitignore b/packages/makesheet/.gitignore
new file mode 100644
index 0000000..d8b83df
--- /dev/null
+++ b/packages/makesheet/.gitignore
@@ -0,0 +1 @@
+package-lock.json
diff --git a/packages/makesheet/CONTRIBUTING.md b/packages/makesheet/CONTRIBUTING.md
new file mode 100644
index 0000000..031b354
--- /dev/null
+++ b/packages/makesheet/CONTRIBUTING.md
@@ -0,0 +1,49 @@
+# Contributing to makesheet
+
+## Code Style
+
+This project follows Airbnb JavaScript style guidelines. Use ESLint to check and fix code style:
+
+```bash
+yarn lint
+yarn lint-fix
+```
+
+## Object Capability (OCap) Discipline
+
+This project follows object-capability discipline to enable secure composition and testing. This means avoiding ambient authority where possible.
+
+### Ambient Authority Pattern
+
+When functions need to access global APIs (like `DriveApp.getFileById`), use dependency injection to allow callers to provide these capabilities:
+
+```js
+function doGet(e, io = {}) {
+    const {
+      getFileById = DriveApp.getFileById,
+    } = io;
+    // ... use getFileById instead of DriveApp.getFileById directly
+}
+```
+
+This pattern provides several benefits:
+
+1. **Testability**: Callers can inject mock implementations for testing
+2. **Attenuation**: Callers can provide restricted versions of capabilities
+3. **Composability**: Functions become more modular and reusable
+4. **Security**: Reduces ambient authority and enables principle of least privilege
+
+### References
+
+For more details on object-capability discipline, see the [Agoric OCap Discipline wiki](https://github.com/Agoric/agoric-sdk/wiki/OCap-Discipline).
+
+## Testing
+
+Since this is Google Apps Script code, we use test functions that can be executed in the Google Apps Script debugger:
+
+1. Create test functions prefixed with underscore (e.g., `_testDoGet`)
+2. Use `console.log` to output test results
+3. Run tests by selecting the test function in the GAS editor and clicking run
+4. View results in the console output
+
+This approach allows testing without external frameworks while maintaining the ability to test core functionality.
\ No newline at end of file
diff --git a/packages/makesheet/README.md b/packages/makesheet/README.md
new file mode 100644
index 0000000..23da340
--- /dev/null
+++ b/packages/makesheet/README.md
@@ -0,0 +1,91 @@
+# makesheet
+
+Google Sheets timestamp service for Make-based workflows.
+
+## Overview
+
+This package provides a Google Apps Script web app that returns the modification timestamp of a Google Sheet. This is useful for Make-based build systems that need to track when a sheet has been modified to trigger downstream processing.
+
+## Setup
+
+1. Install clasp globally (required for deployment, though you could add it as a devDependency if preferred):
+   ```bash
+   npm install -g @google/clasp
+   ```
+
+2. Login to Google Apps Script:
+   ```bash
+   yarn login
+   ```
+
+3. Create a new Google Apps Script project and note the script ID. 
+   [See the Google Apps Script documentation](https://developers.google.com/apps-script/guides/projects) for detailed instructions on creating projects.
+
+4. Update `.clasp.json` with your script ID:
+   ```json
+   {
+     "scriptId": "your-script-id-here",
+     "rootDir": "."
+   }
+   ```
+
+5. Push the code to Google Apps Script:
+   ```bash
+   yarn push
+   ```
+
+6. Deploy as a web app and note the deployment ID:
+   ```bash
+   yarn deploy
+   ```
+   [See the clasp deployment documentation](https://developers.google.com/apps-script/guides/clasp#deployments) for more details on deployment options and web app configuration.
+
+## Usage
+
+Once deployed, you can query the modification time of a Google Sheet using:
+
+```bash
+curl -s "https://script.google.com/macros/s/YOUR_DEPLOYMENT_ID/exec?sheetId=YOUR_SHEET_ID"
+```
+
+This returns a JSON response:
+```json
+{
+  "modifiedTime": "2023-12-01T15:30:45.123Z"
+}
+```
+
+Or an error response:
+```json
+{
+  "error": "sheetId parameter required"
+}
+```
+
+## Integration with Make
+
+Use the provided `example-usage.mk` file as a reference for integrating with Make-based workflows.
+
+## Scripts
+
+- `yarn push` - Push code to Google Apps Script (uploads your local files to the remote project)
+- `yarn deploy` - Push and deploy as web app (requires DEPLOYMENT_ID env var) (creates a new web app version that can be accessed via URL)
+- `yarn curl` - Test the deployed web app (requires DEPLOYMENT_ID and SHEET_ID env vars)
+- `yarn login` - Login to Google Apps Script
+- `yarn lint` - Run ESLint to check code style (Airbnb style)
+- `yarn lint-fix` - Run ESLint and automatically fix issues
+
+## Testing
+
+The code includes test functions that can be used with the Google Apps Script debugger:
+
+- `_testDoGet()` - Tests the main `doGet` function with various input scenarios
+- `_testCreateJsonResponse()` - Tests the JSON response creation function
+
+To run tests in the Google Apps Script editor:
+1. Open your script in the Google Apps Script editor
+2. Select one of the test functions from the function dropdown
+3. Click the run button to execute the test
+4. View the output in the console
+
+This approach follows the pattern suggested for testing Google Apps Script functions without requiring external test frameworks.
\ No newline at end of file
diff --git a/packages/makesheet/appsscript.json b/packages/makesheet/appsscript.json
new file mode 100644
index 0000000..b8a8e97
--- /dev/null
+++ b/packages/makesheet/appsscript.json
@@ -0,0 +1,11 @@
+{
+  "webapp": {
+    "access": "ANYONE_ANONYMOUS",
+    "executeAs": "USER_DEPLOYING"
+  },
+  "timeZone": "America/Chicago",
+  "dependencies": {
+  },
+  "exceptionLogging": "STACKDRIVER",
+  "runtimeVersion": "V8"
+}
diff --git a/packages/makesheet/example-usage.mk b/packages/makesheet/example-usage.mk
new file mode 100644
index 0000000..dd34374
--- /dev/null
+++ b/packages/makesheet/example-usage.mk
@@ -0,0 +1,46 @@
+# Example usage of makesheet package in Makefile workflows
+# 
+# Set these environment variables:
+# DEPLOYMENT_ID = your Google Apps Script deployment ID
+# SHEET_ID = the Google Sheet ID you want to track
+
+# Target file to store the sheet's timestamp
+SHEET_TIMESTAMP_FILE = sheet.timestamp
+
+# URL for the deployed makesheet web app
+SHEET_INFO_URL = https://script.google.com/macros/s/$(DEPLOYMENT_ID)/exec
+
+# Create a timestamp file based on the sheet's last modification time
+$(SHEET_TIMESTAMP_FILE):
+	curl -s "$(SHEET_INFO_URL)?sheetId=$(SHEET_ID)" | \
+	jq -r '.modifiedTime' | \
+	xargs -I {} touch -d {} $@
+
+# Example target that depends on the sheet timestamp
+data-processing: $(SHEET_TIMESTAMP_FILE)
+	@echo "Processing data from sheet (last modified: $$(cat $(SHEET_TIMESTAMP_FILE)))"
+	# Your data processing commands here
+
+# Clean up timestamp file
+clean:
+	rm -f $(SHEET_TIMESTAMP_FILE)
+
+# Check if sheet has been modified since last processing
+check-sheet-status: $(SHEET_TIMESTAMP_FILE)
+	@if [ -f $(SHEET_TIMESTAMP_FILE) ]; then \
+		echo "Sheet timestamp file exists: $$(ls -la $(SHEET_TIMESTAMP_FILE))"; \
+	else \
+		echo "Sheet timestamp file does not exist, will be created"; \
+	fi
+
+# Alternative approach: always check and update if sheet is newer
+update-if-newer:
+	@CURRENT_TIME=$$(curl -s "$(SHEET_INFO_URL)?sheetId=$(SHEET_ID)" | jq -r '.modifiedTime'); \
+	if [ ! -f $(SHEET_TIMESTAMP_FILE) ] || [ "$$(date -r $(SHEET_TIMESTAMP_FILE) -u +%Y-%m-%dT%H:%M:%S.%3NZ)" != "$$CURRENT_TIME" ]; then \
+		echo "Sheet has been modified, updating timestamp"; \
+		echo "$$CURRENT_TIME" | xargs -I {} touch -d {} $(SHEET_TIMESTAMP_FILE); \
+	else \
+		echo "Sheet has not been modified since last check"; \
+	fi
+
+.PHONY: data-processing clean check-sheet-status update-if-newer
diff --git a/packages/makesheet/package.json b/packages/makesheet/package.json
new file mode 100644
index 0000000..e1add2b
--- /dev/null
+++ b/packages/makesheet/package.json
@@ -0,0 +1,23 @@
+{
+  "name": "makesheet",
+  "version": "0.1.0",
+  "description": "Google Sheets timestamp service for Make-based workflows",
+  "author": "Dan Connolly (with GitHub Copilot)",
+  "license": "MIT",
+  "scripts": {
+    "push": "clasp push",
+    "deploy": "clasp push; clasp deploy --deploymentId $DEPLOYMENT_ID",
+    "curl": "curl -L https://script.google.com/macros/s/$DEPLOYMENT_ID/exec?sheetId=$SHEET_ID",
+    "login": "clasp login",
+    "lint": "eslint --config .eslintrc.json --no-eslintrc *.js",
+    "lint-fix": "eslint --config .eslintrc.json --no-eslintrc --fix *.js"
+  },
+  "devDependencies": {
+    "@google/clasp": "^2.3.0",
+    "@types/google-apps-script": "^1.0.17",
+    "typescript": "^4.0.5",
+    "eslint": "^7.32.0",
+    "eslint-config-airbnb-base": "^14.2.1",
+    "eslint-plugin-import": "^2.22.1"
+  }
+}
diff --git a/packages/makesheet/sheetInfo.js b/packages/makesheet/sheetInfo.js
new file mode 100644
index 0000000..4354aca
--- /dev/null
+++ b/packages/makesheet/sheetInfo.js
@@ -0,0 +1,77 @@
+/**
+ * Creates a JSON response for the web app
+ * @param {Object} data - The data to include in the JSON response
+ * @returns {GoogleAppsScript.Content.TextOutput} The JSON response
+ */
+function createJsonResponse(data) {
+  return ContentService.createTextOutput(JSON.stringify(data)).setMimeType(
+    ContentService.MimeType.JSON,
+  );
+}
+
+/**
+ * Main web app handler that returns sheet modification timestamps
+ * @param {GoogleAppsScript.Events.DoGet} e - The GET request event
+ * @param {Object} io - Dependency injection object for testing
+ * @param {Function} io.getFileById - Function to get file by ID (defaults to DriveApp.getFileById)
+ * @returns {GoogleAppsScript.Content.TextOutput} JSON response with timestamp or error
+ */
+function doGet(e, io = {}) {
+  const {
+    getFileById = DriveApp.getFileById,
+  } = io;
+
+  const { sheetId } = e.parameter;
+  if (!sheetId) {
+    return createJsonResponse({ error: 'sheetId parameter required' });
+  }
+
+  try {
+    const file = getFileById(sheetId);
+    const modifiedTime = file.getLastUpdated().toISOString();
+    return createJsonResponse({ modifiedTime });
+  } catch (error) {
+    return createJsonResponse({ error: error.toString() });
+  }
+}
+
+// Test functions for use with Google Apps Script debugger
+/**
+ * Test function for doGet with various scenarios
+ */
+function _testDoGet() {
+  console.log('Testing doGet with missing sheetId...');
+  const resultMissing = doGet({ parameter: {} });
+  console.log('Result:', resultMissing.getContent());
+
+  console.log('Testing doGet with invalid sheetId...');
+  const resultInvalid = doGet({ parameter: { sheetId: 'invalid-id' } });
+  console.log('Result:', resultInvalid.getContent());
+
+  console.log('Testing doGet with mock getFileById...');
+  const mockFile = {
+    getLastUpdated: () => new Date('2023-12-01T15:30:45.123Z'),
+  };
+  const mockIo = {
+    getFileById: () => mockFile,
+  };
+  const resultMock = doGet({ parameter: { sheetId: 'test-id' } }, mockIo);
+  console.log('Result:', resultMock.getContent());
+
+  // Note: To test with a valid sheet ID, replace 'your-test-sheet-id'
+  // with an actual Google Sheets ID you have access to
+  console.log('Testing doGet with valid sheetId (uncomment to test)...');
+  // const resultValid = doGet({ parameter: { sheetId: 'your-test-sheet-id' } });
+  // console.log('Result:', resultValid.getContent());
+}
+
+/**
+ * Test function for createJsonResponse
+ */
+function _testCreateJsonResponse() {
+  console.log('Testing createJsonResponse...');
+  const testData = { test: 'value', timestamp: new Date().toISOString() };
+  const response = createJsonResponse(testData);
+  console.log('Response content:', response.getContent());
+  console.log('Response MIME type:', response.getMimeType());
+}