Frits Zwager

Building safety checks for AI agents that pay. x402 Doctor checks 50,000 paid APIs every day; presign-guard checks transactions before an agent signs.

Amsterdam Joined on Oct 17, 2026 https://fizzl.eu/

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Founder, Fizzl

Frits Zwager

Nov 1

Why does my x402 endpoint fail? A debugging checklist

#x402 #webdev #api #payments

4 min read

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Frits Zwager

Oct 20

XRPL Batch, delegation and MPTs: what an AI agent should check before signing

#xrpl #ai #security #blockchain

3 min read

Frits Zwager

Oct 18

The seven most common x402 seller mistakes, and how to fix them

#x402 #webdev #api #ai

6 min read

Frits Zwager

Oct 17

We check 50,000 paid x402 endpoints every day. Here's what works and what breaks.

#x402 #ai #api #webdev

5 min read

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Frits Zwager

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Why does my x402 endpoint fail? A debugging checklist

Want to connect with Frits Zwager ?

XRPL Batch, delegation and MPTs: what an AI agent should check before signing

The seven most common x402 seller mistakes, and how to fix them

We check 50,000 paid x402 endpoints every day. Here's what works and what breaks.