Uploaded September 2026 | Updated September 2026, 3 weeks ago
Between the moment an x402 server verifies a payment signature and the moment it settles on the blockchain, nothing stops the buyer spending that money somewhere else. Jan Curn's point is that a client can mint a thousand signatures against one wallet, so any seller starting real work on the strength of a verification is exposed. The workaround is to do the work only after settlement, fine for a fixed price API call and awkward for anything slower. Curn is bullish enough on x402 to have shipped it two days before this talk, adding 20,000 Apify tools to a marketplace that previously carried about 2,000, and critical enough to spend the session on what it still gets wrong. He pitches it as a sequel to a talk here last year arguing that MCP was not good yet.
The gaps compound. x402 wants HTTP 402 as the server's first response and MCP wants 401, and since one response cannot be both, companies stand up a second hostname purely for payments. Curn calls that an antipattern and asks how anyone would feel about a separate Amazon for every credit card. The original exact scheme charges a fixed fee per call, which does not fit tools that run for seconds or for hours, and the up to scheme meant to fix metered billing left the double spending window open anyway. Apify settled on charging in full and refunding the remainder, at the cost of a second chain transaction and a trust assumption pointing the wrong way. He is watching batch settlement, and has shipped a markdown page an agent reads to buy a prepaid token, deliberately not an API.
Speaker info:
- https://x.com/jancurn
- linkedin.com/in/jancurn
- apify.com/jancurn
Timestamps:
0:00 - A callback to "MCP isn't good yet"
2:02 - Apify's 45,000 tools, and 10x'ing the x402 catalog
4:47 - The standards pileup, from L402 to Agent Pay
5:39 - Why crypto fits agentic payments, disputes included
8:25 - A 30 year old status code finally picked up
9:19 - The x402 flow, and the double spending window
11:10 - When x402 wants a 402 and MCP wants a 401
12:59 - Exact, then "up to", and what it still did not fix
13:55 - Charging in full, refunding the rest, and batch settlement
16:38 - AGI, an agent general interface
19:26 - Where the volume actually is today
Between the moment an x402 server verifies a payment signature and the moment it settles on the blockchain, nothing stops the buyer spending that money somewhere else. Jan Curn's point is that a client can mint a thousand signatures against one wallet, so any seller starting real work on the strength of a verification is exposed. The workaround is to do the work only after settlement, fine for a fixed price API call and awkward for anything slower. Curn is bullish enough on x402 to have shipped it two days before this talk, adding 20,000 Apify tools to a marketplace that previously carried about 2,000, and critical enough to spend the session on what it still gets wrong. He pitches it as a sequel to a talk here last year arguing that MCP was not good yet.
The gaps compound. x402 wants HTTP 402 as the server's first response and MCP wants 401, and since one response cannot be both, companies stand up a second hostname purely for payments. Curn calls that an antipattern and asks how anyone would feel about a separate Amazon for every credit card. The original exact scheme charges a fixed fee per call, which does not fit tools that run for seconds or for hours, and the up to scheme meant to fix metered billing left the double spending window open anyway. Apify settled on charging in full and refunding the remainder, at the cost of a second chain transaction and a trust assumption pointing the wrong way. He is watching batch settlement, and has shipped a markdown page an agent reads to buy a prepaid token, deliberately not an API.
Speaker info:
- https://x.com/jancurn
- linkedin.com/in/jancurn
- apify.com/jancurn
Timestamps:
0:00 - A callback to "MCP isn't good yet"
2:02 - Apify's 45,000 tools, and 10x'ing the x402 catalog
4:47 - The standards pileup, from L402 to Agent Pay
5:39 - Why crypto fits agentic payments, disputes included
8:25 - A 30 year old status code finally picked up
9:19 - The x402 flow, and the double spending window
11:10 - When x402 wants a 402 and MCP wants a 401
12:59 - Exact, then "up to", and what it still did not fix
13:55 - Charging in full, refunding the rest, and batch settlement
16:38 - AGI, an agent general interface
19:26 - Where the volume actually is today
