Arthur De Los Santos

Co-Founder/CTO @ Rindler (YC S26) |
MIT CS & AI Alum |
Boston • 🇩🇴

[Arthur De Los Santos @_arthurdls_]

We got into @ycombinator!
We:
> Noticed AI can't do things for you on the web (major problem)
> Turned down big tech
> Locked in on this problem
> Applied to YC
> Graduated from MIT
@RindlerAI makes every website work for any agent
If you're building w/ agents, we'd love to chat!

[Arthur De Los Santos @_arthurdls_]

@BlaineGame That's the energy Boston needs! Can't wait to see what comes up in the Fall

[Arthur De Los Santos @_arthurdls_]

Exciting time to be doing a startup

The grind is real, but the results are really rewarding

[Arthur De Los Santos @_arthurdls_]

@mannendri There's so much to learn outside of school, it's pretty exciting

[Arthur De Los Santos @_arthurdls_]

Claude Tip: When doing work such as UI design, I found good results having Opus drive the development with Fable subagents reviewing the final work/giving feedback. Opus working until Fable is satisfied saves a lot on tokens and leverages Fable where it's most useful.

[Ankit Gupta @agupta]

oh shit

[Menlo Times @menlotimes]

Y Combinator @ycombinator Launches of the Week:

(This round-up is for informational purposes only, and in order of the date/time of the launch, from earliest to latest.)

1) Rindler: Founded by Arthur De Los Santos @_arthurdls_ and Michael Serrano @m_y_serrano, Rindler turns any website, including sites without APIs, into a deterministic API that AI agents can reliably use. Know More At: https://t.co/rD9AZkmddi

2) Control Seat: Founded by Jack Grodnick and Warren Shepard, Control Seat is the operating system for the physical world. Know More At: https://t.co/r06MY7F1ry

3) Monumint @monumintcom: Founded by Tyler Maran @TylerMaran and Anna Pojawis, Monumint is Conversational AI purpose-built for financial services. Know More At: https://t.co/8Rb8Oad7UV

4) Litmus: Founded by Shaivi Rau @ShaiviRau and Elena Zhao @ElenaxZhao, Litmus @UseLitmus is the most accurate read on how an engineer actually builds. Know More At: https://t.co/fIELyVjyXj

5) Ekpa: Founded by Anant Asthana and Yuga Patel, Ekpa is building autonomous research agents for trading. Know More At: https://t.co/v0m0DXyeA0

6) Frigade @FrigadeHQ: Founded by Eric Brownrout and Christian Mathiesen, Frigade is an AI-powered product assistance for modern software teams. They have launched Frigade Skills: the in-app AI agent that learns your product and acts for your users. Know More At: https://t.co/85YdZjSQWu

Post: https://t.co/xYLunR0d1j

Source: https://t.co/XNgPMp4yP3

[Arthur De Los Santos @_arthurdls_]

@ycombinator @RindlerAI @m_y_serrano We just launched on YC, appreciate any support here:

https://t.co/5rkw2zmx8V

[Arthur De Los Santos @_arthurdls_]

We got into @ycombinator!
We:
> Noticed AI can't do things for you on the web (major problem)
> Turned down big tech
> Locked in on this problem
> Applied to YC
> Graduated from MIT
@RindlerAI makes every website work for any agent
If you're building w/ agents, we'd love to chat!

[Arthur De Los Santos @_arthurdls_]

Checkout: https://t.co/bejdvbEXNt

[Michael Serrano @m_y_serrano]

Ever tried to automate a real website and ended up babysitting Playwright selectors, browser-use agents, or computer-use agents?

Watch me use Rindler to set up my plans for the world cup ⚽️🏆
https://t.co/Ut39U6aVTm

[Arthur De Los Santos @_arthurdls_]

Fable 5 is out!

[Arthur De Los Santos @_arthurdls_]

@rayanranaut I think X filters each person's feed for what they care about. There's probably a whole other side of @X we haven't seen yet

[Arthur De Los Santos @_arthurdls_]

@boardyai Same

[Arthur De Los Santos @_arthurdls_]

@kumesh_a @speedrun Agents should be able to operate on the web in your behalf efficiently and effectively

We're building https://t.co/bejdvbEpXV (YC S26), the infrastructure layer that sits on top of any website and allows AI agents to action on them in a deterministic way.

[Arthur De Los Santos @_arthurdls_]

What website has the worst UI?

[alisa rae .☘︎ ݁˖ @raealisa]

top 9 worst user experiences of all time:
1. GCP
2. Workday
3. X search
4. Sterling
5. X ads manager
6. Gmail search
7. Any Adobe product
8. Outlook
9. myGov australia

[Arthur De Los Santos @_arthurdls_]

Has anyone tried setting up openclaw to work on the web?

[Arthur De Los Santos @_arthurdls_]

I don't think many people realize how powerful claude can be with /goal

Tried asking it a weird prompt to see what it would do:
/goal make a baked smoothie

Initially, it correctly reasoned that smoothies are blended, not baked, and made some ascii art and ingredients for the smoothie. When claude declared itself done, /goal told claude that it had not met its goal; the user asked for a baked smoothie, not a blended one.

It ended up redoing the ascii into the shape of a baked potato and adjusted the instructions accordingly

The lesson:
Use /goal responsibly

[Polymarket @Polymarket]

BREAKING: U.S. to reportedly lift export controls on Anthropic’s Fable 5 as soon as tonight.

[Arthur De Los Santos @_arthurdls_]

Thoughts on Sonnet 5?

Doesn't quite feel like Opus 4.8 levels but its definitely an upgrade over Sonnet 4.6

[Arthur De Los Santos @_arthurdls_]

@marconoiz Go is pretty good