Browser tools

The Kadmo runtime's browser tools let an MCP client drive the Chrome you already work in, through the Kadmo extension. Every tool and its parameters are on MCP tools; this page is about using them well.

Overview

Browser tools let an AI assistant control your browser directly:

• Navigate to pages
• Click buttons and links
• Fill forms
• Extract content
• Take screenshots

When to Use Browser Tools

Use Case	Approach
Exploring a new site	Use snapshot + direct tools
Repeated automation	Create a workflow
Testing/debugging	Direct tools
AI research tasks	Browser tools + extraction

Core Workflow

1. Navigate

Navigate to https://github.com/trending

Tool: navigate

2. Understand the Page

Take a snapshot of the current page

Tool: snapshot

Returns YAML with element refs:

- main [ref=1]
  - article "Repository" [ref=2]
    - heading "repo-name" [ref=3]
    - link "Star" [ref=4]

3. Interact

Click the element with ref 4

Tool: click with ref: 4

4. Extract Data

Extract the text from the page title

Tool: extract with selector

Snapshot-Based Interaction

The snapshot tool returns element refs that provide reliable targeting:

Getting a Snapshot

The call:

{ "name": "snapshot" }

The answer:

- Page URL: https://example.com
- heading "Welcome" [ref=1]
- button "Get Started" [ref=2]
- textbox "Email" [ref=3]

Using Refs

Refs are more reliable than selectors for dynamic pages:

Click by ref:

{
  "name": "click",
  "arguments": {
    "ref": 2,
    "element": "Get Started button"
  }
}

Type by ref:

{
  "name": "type",
  "arguments": {
    "ref": 3,
    "text": "user@example.com",
    "submit": true
  }
}

Selector-Based Interaction

For workflows or when you know the selector:

CSS Selectors

{
  "name": "click",
  "arguments": {
    "selector": "button.btn-primary"
  }
}

Text Selectors

{
  "name": "click",
  "arguments": {
    "selector": "button:has-text('Submit')"
  }
}

Attribute Selectors

{
  "name": "click",
  "arguments": {
    "selector": "[data-testid='submit-btn']"
  }
}

Scrolling in Containers

For nested scrollable areas (like chat lists):

1. Hover to Position

{
  "name": "hover",
  "arguments": {
    "selector": ".message-list"
  }
}

2. Scroll from Position

{
  "name": "scroll",
  "arguments": {
    "direction": "down",
    "amount": 500
  }
}

The scroll uses the hover position, not viewport center.

Finding Selectors

Using capture_page

Get all interactive elements:

{ "name": "capture_page" }

Returns:

# Page Capture: GitHub

**URL:** https://github.com/trending

## data-testid Selectors
| Selector | Count |
|----------|-------|
| `[data-testid="repo-card"]` | 25 |

## Interactive Elements
| Type | Text | Selector |
|------|------|----------|
| button | Star | `button.star-button` |
| link | Sign in | `a[href="/login"]` |

Using Browser DevTools

1. Right-click element → Inspect
2. Find unique attributes
3. Test selector in console: document.querySelector('...')

Screenshots

Capture the full page:

{ "name": "screenshot" }

Crop to a specific element using its ref from snapshot:

{ "name": "screenshot", "arguments": { "ref": 42 } }

Crop to a CSS selector or manual region:

{ "name": "screenshot", "arguments": { "selector": "#main-form" } }
{ "name": "screenshot", "arguments": { "region": { "x": 0, "y": 0, "width": 800, "height": 400 } } }

Cropped screenshots are 10-100x smaller, saving context tokens. Returns base64-encoded PNG.

Screenshots to a file

Pass path and the PNG is written to disk instead of coming back as image bytes:

{ "name": "screenshot", "arguments": { "selector": "#app", "path": "~/shots/01-dashboard.png" } }

The response is a line of text naming the file and its size — nothing enters your context. Use this for docs screenshots and QA evidence, then hand the file to publish_artifact. The path must resolve inside your home directory.

To redact before capturing, inject CSS first so no unredacted image is ever written. browser_batch runs the whole recipe in one call:

{ "name": "browser_batch", "arguments": { "steps": [
  { "cmd": "navigate", "url": "https://app.example.com/dashboard" },
  { "cmd": "inject_css", "css": ".user-email { filter: blur(6px); }", "id": "redact" },
  { "cmd": "wait", "selector": "#app" },
  { "cmd": "screenshot", "selector": "#app", "path": "~/shots/01-dashboard.png" }
] } }

Example: Research Task

User: Find the top 3 trending Python repositories on GitHub

AI Actions:

1. Navigate to GitHub trending

{ "name": "navigate", "arguments": { "url": "https://github.com/trending/python" }}

2. Snapshot the page

{ "name": "snapshot" }

3. Extract repository names

{ "name": "extract", "arguments": { "selector": ".repo-name" }}

4. Report findings

Example: Form Filling

User: Fill out the contact form on example.com

AI Actions:

1. Navigate

{ "name": "navigate", "arguments": { "url": "https://example.com/contact" }}

2. Snapshot to find form fields

{ "name": "snapshot" }

3. Type into fields

{ "name": "type", "arguments": { "ref": 5, "text": "John Doe" }}
{ "name": "type", "arguments": { "ref": 6, "text": "john@example.com" }}
{ "name": "type", "arguments": { "ref": 7, "text": "Hello, I have a question..." }}

4. Submit

{ "name": "click", "arguments": { "ref": 8, "element": "Submit button" }}

Limitations

What Browser Tools Can't Do

• Actions requiring native popups (file upload dialogs)
• Cross-origin iframe content (some cases)
• Browser-level actions (downloads, extensions)
• Sites with strong anti-automation

Workarounds

Limitation	Workaround
File uploads	Use native automation or manual step
Anti-bot	Use real browser with human verification
iframes	Navigate to iframe src directly if possible

Best Practices

1. Always Snapshot First

Before interacting with a new page:

Take a snapshot so I can see what elements are available

2. Use Refs Over Selectors

Refs from snapshot are more reliable for dynamic pages.

3. Wait for Dynamic Content

If page loads dynamically:

1. Navigate
2. Wait a moment
3. Snapshot

4. Verify Actions

After clicking/typing:

1. Snapshot again
2. Verify page changed as expected

5. Handle Errors Gracefully

If element not found:

1. Re-snapshot
2. Try alternative selector
3. Check if page state changed

Troubleshooting

"Element not found"

1. Snapshot the page to see current structure
2. Verify selector matches
3. Check if element is in iframe
4. Element may be dynamically loaded

"Browser not connected"

The runtime has no extension attached. The tool's answer starts with Browser not connected. and names the fix.

1. Check that the Kadmo extension is installed and its popup says Connected.
2. The extension attaches the first regular tab by itself. If the popup says Not Connected, open a regular web page (not a chrome:// page or the Chrome Web Store) and click Connect.
3. Only one runtime process can hold the extension: if kadmo serve is running, a kadmo mcp started by your client has no browser. See Troubleshooting.

Clicks not working

1. Element may be covered by overlay
2. Try scrolling element into view
3. Check for hover states that must trigger first
4. Use hover before click