WebMCP Checker: Prepare for AI Agent Interactivity

What Is WebMCP?

WebMCP (Web Model Context Protocol) is a W3C standard jointly developed by Google and Microsoft that lets websites expose structured tools and capabilities directly to AI agents in the browser. Instead of agents guessing how to interact with your site, WebMCP provides a structured tool contract.

What Glippy Checks

• Declarative attributes - toolname, tooldescription, and toolparamdescription on forms
• Imperative API - Usage of document.modelContext.provideContext() (and the legacy navigator.modelContext surface, deprecated in Chrome 150)
• SDK/polyfill detection - Whether WebMCP libraries are loaded
• Form agent-readiness - How close your forms are to WebMCP compatibility
• Tool quality - Description completeness and parameter documentation
• Stable element IDs - Whether form IDs are stable rather than dynamically hashed
• Schema.org Action alignment - Whether potentialAction matches your interactive tools

Agent discovery surfaces (new in v1.6)

Beyond WebMCP, Glippy now checks the agent-discovery standards catalogued by specification.website so AI agents can find and call your services:

• MCP server card - /.well-known/mcp/server-card.json
• A2A agent card - /.well-known/agent-card.json
• AP2 payments extension - an Agent Payments Protocol extension declared in the A2A card's capabilities.extensions, for agent-initiated payments with signed Intent/Cart/Payment mandates
• Agent Skills discovery - /.well-known/agent-skills/index.json
• NLWeb endpoint - a natural-language query endpoint advertised via <link rel="nlweb">
• Schemamap - /schemamap.xml listing per-resource JSON-LD endpoints
• Web Bot Auth - an Ed25519 JWKS at /.well-known/http-message-signatures-directory so verifiers (Cloudflare, Akamai, Vercel, AWS WAF) can cryptographically attest your signed agent traffic (RFC 9421 HTTP Message Signatures)

WebMCP and these discovery surfaces are emerging standards, so they are scored as a bonus — present earns credit, absent is surfaced as a tip with no penalty.

WebMCP vs Anthropic's MCP

They are complementary, not competing. Anthropic's MCP is a backend server-to-server protocol. Google's WebMCP is a frontend browser protocol. A complete agent stack might use both: MCP for backend integrations and WebMCP for browser-based interactions.

Should You Implement WebMCP Now?

WebMCP now ships natively in Chromium (Chrome 146+ and Edge 147+), with tools registered via document.modelContext.provideContext() (the deprecated navigator.modelContext surface was removed in Chrome 150). Adoption is still early, so Glippy's Agent Interactivity category keeps a low weight (0.2x) and will not significantly impact your score today. Glippy's Form Agent-Readiness check shows how close your existing forms already are to WebMCP compatibility.