WebMCP Enable

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---
name: webmcp-enable
description: "Add, repair, or verify browser WebMCP tools for a website. Use with editable source or a URL-only site needing a local adapter; covers workflow discovery, native integration, and compatibility diagnosis. Not general scraping or conventional MCP server development."
---

# WebMCP Enable

Turn observed website workflows into useful, discoverable tools without replacing the application. Deliver a working integration for the agreed workflows, with evidence of what the actual browser and client can do. A local adapter changes one browser session, not the hosted website.

## 1. Establish scope and capabilities

Inspect the repository or accessible page, existing registrations, main user journeys, and requested browser/client. Reuse suitable tools already present. For a broad “make this site compatible” request, infer the main workflows from observed routes/forms/actions and state the selected coverage; do not equate one demo tool with whole-site conversion. Ask only about material intent that inspection cannot resolve.

Keep a short working inventory, not a new documentation framework:

| Workflow | Existing implementation | Tool and effect | Completion evidence |
| --- | --- | --- | --- |
| Search | Observed form or search service | Search with filters | Results for this request |
| Checkout | Existing review flow | Prepare checkout; user confirms | Review shown, not “order placed” |

Replace the illustrative rows with actual tasks. Account for each selected workflow as implemented, already supported, or blocked.

Separate **authoring access**, **page-side registration**, and **consumer discovery/invocation**. A browser may expose registration while its page inspector cannot invoke tools; do not disable a usable producer because `getTools` or `executeTool` is absent. Conversely, registration alone proves no client compatibility. Read browser tooling instructions before use; an inspection-only evaluator cannot be used for injection or bypassed via another transport.

Prefer [Source integration](references/source-integration.md) when source is editable; otherwise use [Browser adapters](references/browser-adapters.md). Complete feasible local work even without a test browser, and state the missing verification. Do not invent inaccessible structure or APIs.

## 2. Verify the target contract

Consult the current [WebMCP draft](https://webmachinelearning.github.io/webmcp/) and [browser documentation](https://developer.chrome.com/docs/ai/webmcp) once per target/version. Record date, browser/client versions when available, implementation provenance, and observed capabilities. Report inaccessible docs rather than presenting remembered behavior as verified.

Documentation baseline rechecked **2026-08-31**:

- Current registration is `document.modelContext.registerTool(definition, { signal })`; aborting the registration signal removes the tool. Only add legacy `navigator.modelContext` or `unregisterTool` support for a verified target requiring it; `provideContext`/`clearContext` are not current defaults.
- Where available, discover with `getTools()` and select by name **and owning origin/frame**, never list position or name alone when ambiguous. Feature-detect each capability; an exposed object does not prove policy permits access.
- The draft takes an object in `executeTool(tool, inputObject)`; [Chrome's guide](https://developer.chrome.com/docs/ai/webmcp/imperative-api) still shows JSON text. Resolve the target contract with a harmless representative read-only call; remove any temporary probe tool you registered. Never retry a mutation to guess encoding. If probing is unavailable, leave invocation unverified rather than building a speculative compatibility layer.

WebMCP is not an HTTP/stdio MCP server. A polyfill, extension bridge, or DOM script does not establish native support or connectivity to an arbitrary MCP client. Do not overwrite `document.modelContext` to simulate availability.

## 3. Implemen

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Referenced files: 3 — file references are metadata, not package contents.