Prompt to Add Sitemap and robots.txt to Next.js or Astro

AI agent prompt to add a dynamically generated sitemap.xml and a correct robots.txt to a Next.js or Astro project for better search indexing.

Give this prompt to your agent to add a standards-compliant sitemap.xml and robots.txt — handling dynamic routes, priority values, and lastmod dates without using a paid third-party service.

Main Prompt

You are working in a Next.js 15 App Router project with TypeScript.
The site has static pages (/, /about, /pricing) and dynamic blog posts in `src/content/blog/`.

Task: add sitemap.xml and robots.txt using only Next.js built-in file conventions.

Requirements:
- Create `src/app/sitemap.ts` (NOT `.xml`) using the Next.js `MetadataRoute.Sitemap` return type.
  - Static URLs: `/`, `/about`, `/pricing` with `priority: 1.0` and `changeFrequency: 'monthly'`.
  - Dynamic URLs: read all MDX files from `src/content/blog/` using `getCollection('blog')` from
    `astro:content` — wait, this is Next.js, so use `fs` + `gray-matter` to read frontmatter.
  - For each post, return `{ url, lastModified, changeFrequency: 'weekly', priority: 0.8 }`.
  - `url` must be an absolute URL using the `NEXT_PUBLIC_SITE_URL` environment variable.
- Create `src/app/robots.ts` (NOT `.txt`) using the `MetadataRoute.Robots` return type.
  - Allow all crawlers for `/*`.
  - Disallow `/api/*` and `/admin/*` for all crawlers.
  - Set `sitemap` to the absolute sitemap URL.
- Add `NEXT_PUBLIC_SITE_URL=https://example.com` to `.env.example`.
- Do NOT install `next-sitemap` or any sitemap package.

Stop and list all files before writing code.

Implementation Notes

sitemap.ts and robots.ts in the app/ directory are Next.js 13.3+ file conventions; they must export a default function that returns the typed metadata object — not a Response or string.
If NEXT_PUBLIC_SITE_URL is undefined at build time, the sitemap will contain relative URLs which are invalid per the Sitemap protocol — validate with a startup check.
lastModified should be a Date object, not a string; Next.js serializes it to ISO 8601.

Expected File Changes

src/app/sitemap.ts              (new)
src/app/robots.ts               (new)
src/lib/blog.ts                 (new or edited — getAllPosts helper)
.env.example                    (edited)

Acceptance Criteria

GET /sitemap.xml returns valid XML with all static and dynamic URLs as absolute URLs.
GET /robots.txt includes Disallow: /api/ and Sitemap: https://example.com/sitemap.xml.
Adding a new blog post MDX file causes its URL to appear in the sitemap after bun run build.
The sitemap validates at https://www.xml-sitemaps.com/validate-xml-sitemap.html.

Test Commands

bun run build && bun run start
curl http://localhost:3000/sitemap.xml | xmllint --format - | head -40
curl http://localhost:3000/robots.txt
# confirm /api/ is disallowed and sitemap URL is absolute
bun run typecheck

Common AI Mistakes

Creating a static public/sitemap.xml file instead of the dynamic src/app/sitemap.ts convention.
Using relative URLs in the sitemap (e.g., /blog/my-post) — sitemaps require absolute URLs.
Installing next-sitemap when the prompt explicitly disallows it.
Setting robots.txt to disallow all crawlers (Disallow: /), which de-indexes the entire site.

Fix Prompt

The sitemap contains relative URLs or robots.txt disallows too much. Fix in order:
1. In `src/app/sitemap.ts`, construct every URL as:
   `const base = process.env.NEXT_PUBLIC_SITE_URL ?? 'https://example.com'; url: \`\${base}/blog/\${post.slug}\``
2. In `src/app/robots.ts`, verify the rules object:
   `{ userAgent: '*', allow: '/', disallow: ['/api/', '/admin/'] }`.
3. Confirm `sitemap.ts` exports a default async function (not a named export).
Show only the corrected diff.

Prompt to Add a Sitemap and robots.txt