We probed 2,300+ x402/MPP payable endpoints. Here’s what "payable" actually means in practice

Description and use

We probed over 2,300 x402/MPP payable endpoints and found only 63 % were live, improving AI agent reliability.

Problem

Many services listed as payable via x402/MPP/ACP are dead or outdated, causing AI agents to waste calls on non‑functional endpoints.

Outcome

Out of 2,328 indexed services, 1,472 (63%) were confirmed live, improving agent reliability and reducing wasted calls.

Workflow

• 1. Build an index of all x402/MPP/ACP endpoints from various sources.
• 2. Schedule periodic HTTP probes for each endpoint.
• 3. Verify responses: expect HTTP 402 with a payment challenge or a valid x402/MPP challenge body.
• 4. Mark endpoints as "live" only if they pass the probe.
• 5. Expose the live list via an MCP server for agents to query.

Evidence

Right now: 2,328 services indexed, only 1,472 (~63%) actually live.

Source