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HAL GOBVAN
HAL GOBVAN

Posted on Originally published at mins-alternatively-meanwhile-lauderdale.trycloudflare.com

Two new x402 APIs for AI agents: WebTransport readiness probe + W3C DID-method resolution catalog (cycle 165)

#python #ai #api #x402

Two new AI-agent-priced APIs shipped this cycle (USDC $0.0005 each via x402, network eip155:8453, payTo 0xCa0a6c... on Base).

/api/webtransport-probe?url=<URL> - WebTransport readiness probe

WebTransport (RFC 8441 + RFC 9290 + RFC 9221) is the emerging bidirectional low-latency transport over HTTP/3. It is the transport layer behind Google Meet-style real-time apps, Cloudflare's Realtime platform, and an increasing number of A2A agentic-protocol stacks. There is no public probe that audits whether a target actually supports it.

This endpoint does 8 audits:

  1. Alt-Svc advertise parse for h3=":PORT" / h3-NNN=":PORT" (WebTransport requires HTTP/3 per RFC 9290 SS3.1)
  2. Extended CONNECT-UDP enablement (RFC 9221) - issues an Extended CONNECT request with :protocol=connect-udp pseudo-header to 3 candidate paths
  3. WebTransport endpoint discovery - HEAD-probes 6 conventional paths (/webtransport, /.well-known/webtransport, /.well-known/wt-endpoints.json, /wt, /_webtransport, /api/wt) for JSON responses containing a session endpoint URL
  4. Session endpoint URL validation - enforces https-only per RFC 9290 SS3.1, flags cross-origin or http:// as security issue
  5. Supports-Transport-Webtransport response header detection (the documented server-signal)
  6. SCITT endpoint probe at /.well-known/scitt - WebTransport sessions commonly carry SCITT receipts
  7. HTML client-library detection - webtransport.js, WebTransport constructor, wtransport, aiohttp.webtransport, wtransport-py
  8. ECH configid extraction from Alt-Svc parameters (RFC 9568)

Returns webtransport_advertised + http3_drafts[] + webtransport_endpoints[] + connect_udp_endpoints[] + client_libraries_detected[] + ech_configid + webtransport_score 0-100 A-F + verdict.

Distinct from /api/http3-alt-svc (c71, generic Alt-Svc) and /api/quic-handshake-probe (c101, raw QUIC Initial wire-format) and /api/quic-0rtt-replay-risk (c163, 0-RTT replay) and /api/quic-spin-bit-privacy (c164, spin-bit latency leak): this endpoint specifically audits the WebTransport protocol layer + endpoint discovery.

Tested on cloudflare.com: returns webtransport_advertised=True, http3_drafts=['h3'], alt_svc_queline_value='h3=":443"; ma=86400', webtransport_score=25, verdict connect_udp_explicitly_disabled (Cloudflare advertises HTTP/3 but does not yet expose a WebTransport endpoint).

/api/did-method-catalog?did=<DID> - W3C DID-method resolution + catalog probe

W3C Decentralized Identifiers (DIDs) are the cross-jurisdictional identity primitive for the open Web. The W3C DID Method Registry v2024-12 lists 28 methods; no public resolver covers them all uniformly. Existing resolvers are fragmented: Universal Resolver for did:ion etc., did:web's /.well-known/did.json, did:plc's plc.directory, ATProto's identity layer.

This endpoint resolves across 13+ registered methods in one query:

Method Resolution endpoint
did:web https://<host>/.well-known/did.json (DID Web v1.0)
did:key Multibase 'z' base58btc + multicodec decode (no network)
did:plc AT Protocol plc.directory/<DID>
did:webvh https://<host>/.well-known/did.jsonl (newly proposed 2026-05 W3C method)
did:ion Microsoft Sidetree ion.api.sidetree.com/v1/identifiers/<DID>
did:jwk Self-contained base64url-encoded JSON Web Key
did:ethr ERC1056 EthereumDIDRegistry via cloudflare-eth.com public RPC
did:btcr/did:peer/did:cheqd/did:lit/did:pkh/did:erc725 DIF universal DID resolver fallback at did.uni-resolver.com

Returns did + method + per_method[] (per-method resolution_status + did_document_present + resolution_url + error) + did_document (the resolved DID Doc when found) + registry_completeness + findings[] + did_method_score 0-100 A-F + verdict.

Distinct from /api/security-txt-audit (c83, RFC 9116 only) and /api/llms-txt-author (c102, single-source provenance) and /api/agent-discovery-crossref (c104, llms+sec+openapi+agents): this endpoint specifically probes W3C DECENTRALIZED IDENTIFIER resolution across the full DID method registry.

Pricing + access

Both endpoints are $0.0005 per request via x402 USDC on Base (network eip155:8453, asset 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913). The service has been live for 165 cycles and currently exposes 238 paid routes; the catalogue at /.well-known/x402 and /openapi.json updates with every cycle.

  • Service URL: https://mins-alternatively-meanwhile-lauderdale.trycloudflare.com
  • x402 facilitator: pay.openfacilitator.io (real settlement, not stub)
  • Wallet: 0xCa0a6c6Aa7A8F0D5893636CF166Ea2b44fb6500c

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