diff --git a/.gitignore b/.gitignore
index d23b8bd..c9ad93e 100644
--- a/.gitignore
+++ b/.gitignore
@@ -12,3 +12,6 @@ dist/
 
 # Test results
 test-results.xml
+
+# Build artifacts
+*.tsbuildinfo
diff --git a/CHANGELOG.md b/CHANGELOG.md
index ad3afea..8d8d818 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,20 @@
+## Unreleased
+
+### Documentation
+
+- **PR Guidelines**: Added CHANGELOG requirement to CLAUDE.md (#67)
+  - All pull requests must now update CHANGELOG.md
+  - Document what changed, why, and any breaking changes
+  - Add entry under "Unreleased" section with PR number
+
+### Developer Experience
+
+- **Release Process**: Added automated CHANGELOG preparation script (#67)
+  - New `npm run changelog:prepare-release <version>` command
+  - Automatically replaces "Unreleased" with version and date
+  - Adds new empty "Unreleased" section for next changes
+  - Includes validation for version format and CHANGELOG structure
+
 ## 0.4.7
 
 ### Security
diff --git a/CLAUDE.md b/CLAUDE.md
index d8c4ae9..8ea694e 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -77,6 +77,36 @@ Generates three files: `*.input.schema.ts`, `*.output.schema.ts`, and `*.test.ts
 - Never update snapshots without verifying changes
 - Tool snapshots capture class names, tool names, and descriptions
 
+**Pull Requests:**
+
+When creating pull requests:
+
+- **Always update CHANGELOG.md** - Document what changed, why, and any breaking changes
+- Follow the existing changelog format (check recent entries for examples)
+- Add your entry under the "Unreleased" section at the top
+- Include the PR number and a brief description of the change
+
+**Release Process:**
+
+When preparing a new release:
+
+```bash
+# Prepare CHANGELOG for release (replaces "Unreleased" with version and date)
+npm run changelog:prepare-release 1.0.0
+
+# Review changes, then commit and tag
+git add CHANGELOG.md
+git commit -m "Release v1.0.0"
+git tag v1.0.0
+git push && git push --tags
+```
+
+The `changelog:prepare-release` script automatically:
+
+- Replaces "## Unreleased" with "## {version} - {date}"
+- Adds a new empty "## Unreleased" section at the top
+- Validates version format and CHANGELOG structure
+
 ## Important Constraints
 
 - **Tool naming:** Tool names (MCP identifiers) must be `snake_case_tool` (e.g., `list_styles_tool`). TypeScript class names follow `PascalCaseTool` convention (e.g., `ListStylesTool`)
diff --git a/package.json b/package.json
index 9db4559..24a69dd 100644
--- a/package.json
+++ b/package.json
@@ -12,6 +12,7 @@
   "scripts": {
     "postinstall": "patch-package || true",
     "build": "npm run prepare && tshy && npm run generate-version && node scripts/add-shebang.cjs",
+    "changelog:prepare-release": "node scripts/prepare-changelog-release.cjs",
     "format": "prettier --check \"./src/**/*.{ts,tsx,js,json,md}\" \"./test/**/*.{ts,tsx,js,json,md}\"",
     "format:fix": "prettier --write \"./src/**/*.{ts,tsx,js,json,md}\" \"./test/**/*.{ts,tsx,js,json,md}\"",
     "generate-version": "node scripts/build-helpers.cjs generate-version",
diff --git a/scripts/prepare-changelog-release.cjs b/scripts/prepare-changelog-release.cjs
new file mode 100755
index 0000000..595254a
--- /dev/null
+++ b/scripts/prepare-changelog-release.cjs
@@ -0,0 +1,81 @@
+#!/usr/bin/env node
+// Copyright (c) Mapbox, Inc.
+// Licensed under the MIT License.
+
+/**
+ * Prepares CHANGELOG.md for a new release by:
+ * 1. Replacing "## Unreleased" with "## {version}"
+ * 2. Adding current date to the version heading
+ * 3. Adding a new empty "## Unreleased" section at the top
+ *
+ * Usage:
+ *   node scripts/prepare-changelog-release.cjs <version>
+ *   npm run changelog:prepare-release <version>
+ *
+ * Example:
+ *   node scripts/prepare-changelog-release.cjs 1.0.0
+ */
+
+const fs = require('node:fs');
+const path = require('node:path');
+const process = require('node:process');
+
+function prepareChangelogRelease(version) {
+  if (!version) {
+    console.error('Error: Version number is required');
+    console.error('Usage: node scripts/prepare-changelog-release.cjs <version>');
+    process.exit(1);
+  }
+
+  // Validate version format (basic semver check)
+  if (!/^\d+\.\d+\.\d+(-[a-zA-Z0-9.-]+)?$/.test(version)) {
+    console.error(`Error: Invalid version format: ${version}`);
+    console.error('Expected format: X.Y.Z or X.Y.Z-prerelease');
+    process.exit(1);
+  }
+
+  const changelogPath = path.join(process.cwd(), 'CHANGELOG.md');
+
+  // Check if CHANGELOG.md exists
+  if (!fs.existsSync(changelogPath)) {
+    console.error('Error: CHANGELOG.md not found');
+    process.exit(1);
+  }
+
+  // Read CHANGELOG.md
+  const content = fs.readFileSync(changelogPath, 'utf8');
+
+  // Check if "## Unreleased" exists
+  if (!content.includes('## Unreleased')) {
+    console.error('Error: No "## Unreleased" section found in CHANGELOG.md');
+    console.error('Nothing to release - add changes under "## Unreleased" first');
+    process.exit(1);
+  }
+
+  // Get current date in YYYY-MM-DD format
+  const date = new Date().toISOString().split('T')[0];
+
+  // Replace "## Unreleased" with "## {version} - {date}"
+  // and add a new "## Unreleased" section at the top
+  const updatedContent = content.replace(
+    '## Unreleased',
+    `## Unreleased\n\n## ${version} - ${date}`
+  );
+
+  // Write updated content back to CHANGELOG.md
+  fs.writeFileSync(changelogPath, updatedContent, 'utf8');
+
+  console.log(`✓ CHANGELOG.md updated successfully`);
+  console.log(`  - Released version ${version} (${date})`);
+  console.log(`  - Added new "Unreleased" section`);
+  console.log('');
+  console.log('Next steps:');
+  console.log('  1. Review CHANGELOG.md');
+  console.log('  2. Commit changes: git add CHANGELOG.md && git commit -m "Release v' + version + '"');
+  console.log('  3. Create tag: git tag v' + version);
+  console.log('  4. Push: git push && git push --tags');
+}
+
+// Process command line arguments
+const version = process.argv[2];
+prepareChangelogRelease(version);