This Week in Extensibility: MCP's spec locks down its auth and skills, WebMCP gets conformance tests, WebAssembly components bind to real-world interfaces

2026-07-10T00:00:00-04:00

The connective layer for agent-driven software kept maturing this week. MCP's next specification entered its final editing pass ahead of a July 28 launch, this time reworking how a user's client authenticates to servers and adding a way to distribute agent skills. WebMCP gained its first cross-vendor conformance suite, Apple introduced a first-party way for agents to drive Safari, and in the runtime layer the WebAssembly Component Model moved to bind components to real-world interfaces.

Protocols: MCP's next spec locks down its auth and skills pieces

MCP's 2026-07-28 specification entered its final editing pass. On July 10 the project pushed a burst of finalization commits as the spec moved toward its scheduled July 28 launch. The leaner stateless core and mid-run Multi Round-Trip Requests were covered in prior weeks; the fresh changes this week are about authentication and distribution. The draft deprecates OAuth Dynamic Client Registration in favor of Client ID Metadata Documents, changing how a user's client identifies itself to the servers it connects to. Alongside it, a draft Skills extension defines a skill:// convention for serving reusable agent skills over MCP, with reference implementations named across Claude Code, goose, codex, gemini-cli, and the GitHub MCP server.

Why it matters: the specification is a release candidate scheduled to launch July 28, not final. What changed this week is at the protocol's edges, not its core. The client-auth model now leans on metadata documents instead of dynamic registration, and the Skills convention standardizes how an agent's skills are packaged and shared. Both are still draft.

Agentic web: a conformance suite, and a first-party browser server

WebMCP published a public conformance test suite. On July 10 the W3C Web Machine Learning Community Group added a web-platform-tests suite for WebMCP, the protocol that lets a website expose in-page tools for a user's agent to call. A shared test suite is the first cross-vendor step toward measuring interoperability. It remains a Community Group draft with no shipping stable browser: the capability is in a Chrome origin trial, an experiment, not a default. Design work continued alongside, including an open proposal for a machine-readable hint that marks an action as easily reversible so a user's agent can skip confirmation on low-consequence steps.

Apple introduced a first-party Safari MCP server. On July 1, WebKit shipped a Safari MCP server in Safari Technology Preview 247 that connects an agent to a live Safari window with access to the DOM, network requests, screenshots, and console output, plus the ability to evaluate JavaScript and click, type, and scroll. It is aimed at web developers debugging their own sites and ships only in the preview build, not stable Safari.

Why it matters: two mechanisms for pointing an agent at the browser advanced in the same week. With WebMCP, a page exposes tools to the agent; Apple's server drives the browser from the outside through safaridriver. Neither is a shipped consumer capability yet. WebMCP is an early draft in a single-vendor origin trial, and the Safari server is a developer-facing preview.

Runtime: the WebAssembly Component Model binds to real-world interfaces

The WebAssembly Component Model added external-id and implements. A change merged July 8 lets a component's imports and exports bind to arbitrary external identifiers, e.g., URLs, ES module specifiers, or named host instances like redis, instead of only the kebab-case names the interface language allows. It was demonstrated with experimental Wasmtime support at the July 9 WASI call.

Why it matters: the Component Model is the layer that produces portable, sandboxed plugins. Letting components declare that they implement a real-world interface, rather than a name invented for the spec, is a step toward wiring Wasm plugins against the host systems they actually target. This is pre-standard, implemented experimentally in the reference runtime.

Also worth knowing

Standard Webhooks hardened its client libraries to reject empty signing secrets on July 7, a small cross-vendor guard against a common misconfiguration in the convention many vendors use to sign webhook payloads.

A request for WebKit's position on handle_links was filed July 5. The manifest member would let an installed web app declare whether links opened from outside it route into the app or a browser tab. No WebKit position is recorded yet.

Merge.dev gave its embedded agent handler generic Salesforce CRUD, letting customer-facing agents read and write any Salesforce object rather than a fixed set, a modest widening of what an embedded agent can do inside a customer's connected app.

The sandbox market (E2B, Modal, Daytona, Cloudflare) was quiet at the capability level, as were the webhook and URL-scheme standards beyond the item above and the malleable-software community.

On the radar

July 12–14: Local-First Conf 2026, Berlin, theme "user empowerment in an age of fluid software."
July 16: Next W3C WebExtensions Community Group meeting.
July 23: Next W3C WebExtensions Working Group meeting.
July 28: Target launch date for the MCP 2026-07-28 specification; the release candidate and beta SDKs are already out.