# emin.de

> emin.de publishes long-form written work by Emin Mahrt on Bitcoin self-custody, payment rails, AI agents and the engineering behind them. Every post is plain Markdown in a public GitHub repository and is served as HTML, Markdown, JSON, feeds and through a public MCP server.

Long-form engineering writing, built to be read by people and agents. Written by Emin Mahrt.

## Latest posts

- [Build your own Nuri card](https://emin.de/posts/build-your-own-nuri-card) (2026-10-30, guide, Emin Mahrt.) One blank card carries passkeys, an SSH key, a bitcoin cosigner and a vault. Full build with real commands, plus a Tangem, YubiKey and Bitkey comparison. Markdown: [index.md](https://emin.de/posts/build-your-own-nuri-card/index.md)
- [I built a Chrome extension to control my browser location](https://emin.de/posts/fake-location-chrome-spotify-family) (2026-10-30, guide, Emin Mahrt.) A small Chrome and Brave extension that overrides navigator.geolocation, why it alone did not fix a Spotify Family country mismatch, and what it cannot touch. Markdown: [index.md](https://emin.de/posts/fake-location-chrome-spotify-family/index.md)
- [How to make a music video with Claudia](https://emin.de/posts/how-to-make-a-claudia-music-video) (2026-10-30, guide, Emin Mahrt.) A complete making-of: the open character Claudia, a song map, 16:9 scene plates, target-audio lip sync, the edit, the subtitles and every version I made, including the failures. Markdown: [index.md](https://emin.de/posts/how-to-make-a-claudia-music-video/index.md)
- [Who goes to jail when the agent does it?](https://emin.de/posts/who-goes-to-jail-when-the-agent-does-it) (2026-10-30, essay, Emin Mahrt.) My agent bought DHL postage for an eBay sale. Who is responsible when an agent acts, and why hard wallet limits are a better answer than blame after the fact. Markdown: [index.md](https://emin.de/posts/who-goes-to-jail-when-the-agent-does-it/index.md)
- [An agent can pick up the phone](https://emin.de/posts/an-agent-can-pick-up-the-phone) (2026-10-28, essay, Emin Mahrt.) A real phone on the desk, two hundred tyre shops, and a wallet with a small budget. What it takes before an agent can do one boring job for money. Markdown: [index.md](https://emin.de/posts/an-agent-can-pick-up-the-phone/index.md)
- [Learning to fly in Tanzania, plus my small PPL study app](https://emin.de/posts/learning-to-fly-tanzania-ppl-app) (2026-10-28, guide, Emin Mahrt.) I compared Tanzania's five beginner flight school options, checked the German conversion rules and built a free PPL(A) app with 90 original questions. Markdown: [index.md](https://emin.de/posts/learning-to-fly-tanzania-ppl-app/index.md)
- [Let ChatGPT make a real phone call](https://emin.de/posts/let-chatgpt-make-a-real-phone-call) (2026-10-28, guide, Emin Mahrt.) A live demo: the free version of ChatGPT calls a tyre shop, asks for winter tyres, price and a slot, and reports back. How the call tool works, and how your agent can use it. Markdown: [index.md](https://emin.de/posts/let-chatgpt-make-a-real-phone-call/index.md)
- [My agent needs tools, not more subscriptions](https://emin.de/posts/my-agent-needs-tools-not-subscriptions) (2026-10-28, essay, Emin Mahrt.) Why I want agents to buy useful tools one job at a time, what Bitcoin has to do with it, and why building faster does not remove my responsibility. Markdown: [index.md](https://emin.de/posts/my-agent-needs-tools-not-subscriptions/index.md)
- [Just add any Nuri user](https://emin.de/posts/fueg-einfach-irgendeinen-nuri-user-hinzu) (2026-10-18, essay, Emin Mahrt.) Referrals, guardians, inheritance, multisig and saving together all become one feature at Nuri. You add a username in the settings, and everything else follows from that. Markdown: [index.md](https://emin.de/posts/fueg-einfach-irgendeinen-nuri-user-hinzu/index.md)
- [One who toils in the sun eats in the shade](https://emin.de/posts/photo-dappled-shade-portrait-bare-shoulder-evening) (2026-10-18, photo, emin.de AI Desk. AI-written, human-supervised: not yet reviewed.) A look back over a bare shoulder in leaf shade, read closely. Real E-M5 II EXIF, 1/320 s at ISO 100, a lens with no name, measured sun patches, 12 June history and one fix. Markdown: [index.md](https://emin.de/posts/photo-dappled-shade-portrait-bare-shoulder-evening/index.md)

## For agents

- [llms.txt](https://emin.de/llms.txt): the site map for language models.
- [RSS](https://emin.de/rss.xml), [Atom](https://emin.de/atom.xml), [JSON Feed](https://emin.de/feed.json).
- [JSON API](https://emin.de/api/articles): every post, no credentials.
- [Developer docs](https://emin.de/developers): API, MCP and examples.