webmcp-gen

Original：🇺🇸 English

Translated

4 scripts

Create, compile, and validate site-specific WebMCP init scripts from a target URL and desired tool capability. Use when the user wants to author WebMCP tools for a website, produce a webmcp.init.js artifact, or test WebMCP registration and invocation through Stagehand.

3installs

Sourcebrowserbase/skills

Added on2026-08-20

NPX Install

npx skill4agent add browserbase/skills webmcp-gen

SKILL.md Content

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WebMCP Gen

Author website-specific WebMCP tools by writing a manifest, compiling it to an init script, and validating that Chrome registers and invokes the tools.

This skill does not call a nested agent. You are responsible for exploring the page, writing

manifest.json

, and iterating based on validation output.

Setup check

From the skill directory, install dependencies if they are not already installed:

bash

cd skills/webmcp-gen
pnpm install

This installs the pinned Stagehand package plus the TypeScript toolchain (

tsx

,

typescript

,

@types/node

) used to run the generated

stagehand-example.ts

.

Workflow

Pick an artifact slug with exactly one slash:

text

<domain>/<task>

Example:

text

example.com/page-context

Scaffold the artifact:

bash

node scripts/scaffold.mjs example.com/page-context --url https://example.com

Explore the target page with the
```
browse
```
CLI:

bash

browse open https://example.com --local
browse snapshot
browse get title
browse get url
browse get text body
browse get html body

Prefer

browse snapshot

, page text, and DOM inspection over screenshots unless visual layout matters. Use

browse stop

when exploration is complete.

Edit
```
artifacts/<domain>/<task>/manifest.json
```
. The manifest is the source of truth.
Compile:

bash

node scripts/compile.mjs artifacts/example.com/page-context

Generate a runnable Stagehand example (
```
stagehand-example.ts
```
) and run it with
```
tsx
```
:

bash

node scripts/generate-stagehand-example.mjs artifacts/example.com/page-context
npx tsx artifacts/example.com/page-context/stagehand-example.ts

Validate:

bash

node scripts/validate.mjs artifacts/example.com/page-context

If validation fails, inspect
```
eval.json
```
and
```
eval-report.md
```
, patch
```
manifest.json
```
, then compile and validate again.

Manifest contract

json

{
  "domain": "example.com",
  "task": "page-context",
  "url": "https://example.com",
  "generatedAt": "2026-06-04T00:00:00.000Z",
  "tools": [
    {
      "name": "example_com_page_context",
      "description": "Returns page context.",
      "inputSchema": {
        "type": "object",
        "properties": {},
        "required": []
      },
      "implementation": {
        "kind": "dom",
        "source": "return { success: true, title: document.title, url: location.href };"
      },
      "fixtureInput": {}
    }
  ]
}

Authoring rules

```
implementation.source
```
is inserted inside
```
async (input) => { ... }
```
; write JavaScript statements, not a full function wrapper.
Return a JSON-serializable object.
WebMCP code runs inside the browser page. Use browser-native APIs:
```
document
```
,
```
location
```
,
```
navigator
```
, and same-origin
```
fetch
```
.
Do not use Playwright, Puppeteer, Stagehand, XPath helpers, or agent/browser commands inside
```
implementation.source
```
.
```
document.querySelector
```
and
```
querySelectorAll
```
must receive valid browser CSS selectors only.

To find visible text, use

Array.from(document.querySelectorAll(...)).find((el) => (el.textContent || "").includes("..."))

.

Do not include API keys, bearer tokens, cookies, localStorage secrets, or user credentials.
Do not use
```
eval
```
or
```
new Function
```
.
Avoid destructive actions unless the user explicitly asked for them.
Make implementations defensive: check for missing elements and return structured
```
{ success: false, error: "..." }
```
responses.
Generated init scripts register WebMCP tools only in the top frame.

Output layout

text

artifacts/<domain>/<task>/
  manifest.json
  webmcp.init.js
  stagehand-example.ts
  eval.json
  eval-report.md

To turn the example into a standalone project, scaffold a Stagehand app with

npx create-browser-app

and drop the generated

webmcp.init.js

into it (load it with

page.addInitScript({ path: "webmcp.init.js" })

).

webmcp-gen

NPX Install

Tags

SKILL.md Content

WebMCP Gen

Setup check

Workflow

Manifest contract

Authoring rules

Output layout