Xcode MCP vs CLI: Where did all the tokens go? | Not only Swift - Issue 108
Hey everyone,
My stream is full of two things: people writing about the iPhone Duo and people writing about how to save tokens.
So in this issue of the newsletter, we’ll have a little bit of both: a few articles that explain how to use some of the fun new features of the iPhone Duo, along with a couple of neat examples (I really like the mini typewriter).
And then we look at agentic engineering. It’s definitely interesting to see the impact this is having on our engineering processes.
Just today, I was talking to someone who told me about a large-scale system migration and the struggles they are having ensuring that their agentic pipelines actually fully convert the legacy application to a more modern one.
On a small scale, AI is amazing, but once projects grow, the scaling issues become very real as well.
I’m looking forward to hearing more stories at the Agentic Hamburg meetup, which will take place at the Google office in Hamburg on November 3rd.
Until then,
Peter
AI multiplied the amount of code your team writes. The process that ships it hasn’t changed: same release trains, same quality gates, same manual handoffs. Join a live panel with mobile engineering leaders from Thomson Reuters, Mercado Libre and Salesforce on what that volume changes about the release process. Nov 12, 10am PT / 1pm ET.
The most obvious thing about a mobile device is the screen - or in the case of an iPhone Duo, its three screens - but even more exciting are all the sensors mobile devices pack. People have used sensors like the gyroscope or the microphone for fun and innovative interactions in the past (like TableDrum, which turned your desk and coffee mug into a drum kit by listening to taps through the microphone). Now, the iPhone Duo adds a hinge sensor that tells us the angle at which the hinge is opened, which makes for some really neat tactile interactions. Natalia explains how it works.
It’s always great to get a behind-the-scenes glimpse of a popular application. In this article, Alexander shares his experience updating the popular Pocket Casts podcast player to support iPhone Duo, from using Apple’s built-in Xcode skill to creating a test suite that exercises the entire application in just a few hours. It’s a great read that wraps up with a couple of practical tips and tricks.
Skills have two main responsibilities:
- filling in the gaps in the model’s knowledge
- teaching the model your preferences
Since models get “smarter” with every new release, filling in the blanks is a moving target. Something you had to teach the model because it happened after the knowledge cutoff might already be included in a newer release of the model.
That’s why SDK providers like Android and Firebase have to keep their skills up to date with the most recent model releases, and run evals to verify they’re actually making a difference.
And since taste is something that is rather subjective, that’s something you’d probably want to keep in cross-cutting skills in the long run, or move it into your AGENTS.md file.
Agentic Software Engineering looks an awful lot like the waterfall process: you spend a lot of time on planning and writing specifications, but a lot less on the actual implementation.
I agree with Joe Fabisevich: it might have a similar shape to waterfall, but since the feedback cycle is so short, it’s typically not a problem.
Are CLIs more efficient to use than MCPs? Or is the model itself capable enough to figure it out? Esther decided to find out by building and deploying an app that helps her optimise her bike riding, “But is it Aero”.
Seems like everybody is dissing MCP servers, at least in terms of token consumption. Here is Antoine explaining how Xcode’s MCP server consumes more tokens than the RocketSim CLI.
This application makes creative use of the hinge angle to detect how far a piece of paper in the typewriter should be extended. It’s just one of the fun things people build when a new form factor arrives.
Mert is not only the creator of the fantastic Franzbrötchen app, he also writes lovely, well-researched articles about Hamburg.
No matter if you live in Hamburg, or you’re planning to come for a visit, you should install Mert’s app and read his articles (best with a warm Franzbrötchen and a coffee).
I had the chance to try out the iPhone Duo in the Apple Store just today, and tiny is exactly the right word for the size of the keys on those retro computers when you run the app on the physical device.
The original iPod is celebrating its 25th anniversary, and Apple marked the occasion by launching a fully functional iPod (preloaded with a collection of songs and the original games) as an interactive 404 page!
Put something in my tip jar. Thanks!
Did you know you can let me know what you're most interested in? Update your preferences - this will help me write what you love reading!
