# Emerging Protocols Checker Check domain-level protocol discovery signals for AI agents, APIs and agentic commerce. ## Why emerging protocols matter Agents need more than readable pages. Some services expose machine-readable ways to discover APIs, authorization metadata, tools, skills, other agents and commerce capabilities. These protocols sit at different maturity levels, so the useful question is not whether every site has every protocol, but whether the protocols relevant to the service are discoverable and implemented according to their current specification. For a broader audit that also checks robots.txt, sitemap discovery, Markdown negotiation and bot controls, use the Site Agent Readiness Checker: https://www.hota.digital/t/site-agent-readiness-checker ## FAQ ### What does the Emerging Protocols Checker do? The checker probes a public domain for machine-discoverable protocol endpoints and static implementation signals used by AI agents, API clients and agentic commerce systems. It checks established standards such as OAuth metadata and API Catalog alongside newer conventions such as MCP Server Cards, Agent Skills discovery, ARD, auth.md, UCP and WebMCP hints. ### What are emerging protocols in the agentic web? Emerging protocols are machine-readable conventions that help agents discover capabilities, authenticate, select tools, interact with other agents or transact with services. Some are published IETF RFCs, some are stable protocol specifications, and others are drafts or proposals. They should not all be treated as equally mature or equally necessary. ### How should I read Detected, Signal, Not detected and Manual check? Detected means the checker found a documented endpoint or structured response that matches the expected protocol shape. Signal means static evidence suggests an implementation but runtime or resource-level validation would still be needed. Not detected means the common discovery location was not found. Manual check means the protocol does not currently expose a universal domain-level endpoint that this server-side checker can reliably verify. ### Does a website need every protocol listed here? No. A content website may need none of them. An API service may care about OAuth, API Catalog or MCP. An agent service may care about A2A or Agent Skills. A commerce business may care about UCP, ACP, x402 or MPP. Use the output as a relevance map, not as a checklist that every site must complete. ### Why are RFC 8414, RFC 9727 and RFC 9728 treated differently from drafts? Those documents are IETF Standards Track RFCs with stable normative requirements. MCP Server Card, Agent Skills discovery, WebMCP and ARD are at different stages of development. The tool shows maturity explicitly so a missing experimental capability is not presented as equivalent to a missing established metadata standard. ### What is OAuth Protected Resource Metadata and why does it matter to agents? RFC 9728 lets a protected resource publish metadata at a predictable well-known location, including the resource identifier and authorization servers that can be used with it. This can reduce manual configuration when an agent or client needs authenticated access to a protected service. ### What is API Catalog? RFC 9727 defines /.well-known/api-catalog and the api-catalog link relation so machines can discover a publisher's public APIs and metadata about them. It is useful when a service wants agents and other clients to find APIs without relying only on human documentation. ### What is an A2A Agent Card? The A2A protocol requires servers to make an Agent Card available. The well-known URI strategy uses /.well-known/agent-card.json. The card describes identity, capabilities, skills and supported interaction protocols so other agents can decide whether and how to connect. ### What is an MCP Server Card? MCP Server Cards are a draft discovery mechanism proposed in SEP-1649 for HTTP MCP servers. The proposal uses a well-known JSON document to describe the server before a full MCP connection is opened. Because the MCP working group is still evolving this area, the checker labels it Draft rather than a stable requirement. ### What is Agent Skills discovery? Agent Skills are an open format built around SKILL.md files. A separate draft from Cloudflare proposes /.well-known/agent-skills/index.json so organizations can publish an index of skills for machine discovery. The Skills format and the domain-level discovery draft should be understood as related but distinct layers. ### What is WebMCP and why can this tool only detect hints? WebMCP is a draft browser API that lets pages register tools through document.modelContext and related interfaces. Because tools can be registered dynamically after JavaScript runs, a server-side HTTP fetch cannot prove runtime support. The checker therefore reports static source hints and recommends browser-level verification. ### What are UCP, ACP, x402 and MPP? They address different parts of agentic commerce. UCP publishes business capabilities through a well-known profile. ACP defines checkout APIs and capability negotiation. x402 uses HTTP 402 for internet-native payment flows. MPP provides machine-payment flows and can advertise payment offers in OpenAPI metadata. Their discovery models and maturity differ, so the checker does not reduce them to one generic commerce score. ### How is this different from the Site Agent Readiness Checker? This tool goes deep on protocol discovery and explains the maturity and meaning of each protocol. The Site Agent Readiness Checker is broader and also covers robots.txt, sitemap discovery, Markdown content negotiation, bot controls and other AI-readiness layers. Use this checker for protocol detail and the broader checker for an overall site review. ### Can this tool prove that an agent can successfully use the detected service? No. Discovery is only the first layer. The checker does not authenticate, execute MCP tools, run A2A tasks, invoke WebMCP in a browser, complete checkout or send payments. A detected descriptor can still be incomplete or point to a service that fails at runtime.