@mozilla/firefox-devtools-mcp
io.github.mozilla/firefox-devtools-mcp · version 0.10.7 · 7,683 weekly npm downloads · audited 2026-11-03
Notes
Findings
No hidden-instruction or invisible-character findings in any tool, prompt, or resource description.
Claude Connectors Directory readiness
- ❌ Every tool has a title Missing on 35 of 35: list_pages, new_page, navigate_page, select_page and 31 more
- ❌ Every tool declares readOnlyHint or destructiveHint Missing on 2 of 35: clear_downloads, set_download_behavior
- ✅ Tool names are 64 characters or fewer All within limit
- ❌ Descriptions avoid instructions about model behavior or other tools 6 of 35 descriptions reference other tools or tell the model what it must do: press_key, type_text, uninstall_extension, screencast_start and 2 more
- ✅ No hidden instructions or invisible characters in tool metadata None found
Checks the directory's published tool requirements that are visible from tools/list. Passing them does not guarantee acceptance.
What this server's tools can do
- Makes outbound web requests:
navigate_page,set_download_behavior,navigate_history
Not a vulnerability by itself. It tells you what an injected prompt could ask this server to do, so you can decide which tools need approval.
Supply chain
- Install scripts: none
- npm provenance: yes
- Source repository linked: yes
- License: MIT OR Apache-2.0
- Direct dependencies: 5
Tools (35)
| Name | Title | Hint | Description |
|---|---|---|---|
list_pages | read-only | List open tabs (index, title, URL). Selected tab is marked. | |
new_page | writes | Open new tab at URL. Returns tab index. | |
navigate_page | writes | Navigate selected tab to URL. | |
select_page | writes | Select active tab by index, URL, or title. Index takes precedence. | |
close_page | writes | Close tab by index. | |
get_page_text | read-only | Get the visible text of the page (document.body.innerText). Caps at maxLength (default 20000 chars); saveTo saves the full text to a file. | |
take_snapshot | read-only | Capture DOM snapshot with stable UIDs. A UID stays valid across snapshots until its element is removed or the page navigates. Output caps at maxLines (default 100); scope with selector or dump the full tree with saveTo. | |
resolve_uid_to_selector | read-only | Resolve UID to CSS selector. Fails if the element is gone. | |
clear_snapshot | writes | Clear snapshot UIDs. Usually not needed. | |
click_by_uid | writes | Click element by UID. Set dblClick for double-click. | |
hover_by_uid | writes | Hover over element by UID. | |
fill_by_uid | writes | Fill text input/textarea by UID. | |
drag_by_uid_to_uid | writes | Drag element to another (HTML5 drag events). | |
fill_form_by_uid | writes | Fill multiple form fields at once. | |
upload_file_by_uid | writes | Upload file to file input by UID. | |
press_key | writes | Press a single key, optionally with modifiers, to submit, dismiss, navigate or trigger a shortcut. Not for entering text: use fill_by_uid instead. | |
type_text | writes | Type text key by key into the focused element, optionally followed by a key such as Enter. Use fill_by_uid to set the value of a known input; use this for elements that only react to real typing, such as autocomplete fie… | |
screenshot_page | read-only | Capture viewport screenshot as base64 PNG. Set fullPage for the whole scrollable document. | |
screenshot_by_uid | read-only | Capture element screenshot by UID as base64 PNG. | |
print_page | read-only | Print the current page to a PDF file using print CSS. Returns the saved file path. | |
list_downloads | read-only | List downloads tracked since startup, including status and saved file path. | |
clear_downloads | none | Clear the tracked downloads buffer. | |
set_download_behavior | none | Control how downloads are handled: allow (save to a destination folder), deny (cancel), or reset to default. Avoids the native save-file dialog. Requires a recent Firefox. | |
accept_dialog | writes | Accept browser dialog. Provide promptText for prompts. | |
dismiss_dialog | writes | Dismiss browser dialog. | |
navigate_history | writes | Navigate history back/forward. UIDs become stale. | |
set_viewport_size | writes | Set viewport dimensions in pixels. Applies to the selected tab only. | |
get_firefox_output | read-only | Retrieve Firefox output (stdout/stderr including MOZ_LOG, warnings, crashes, stack traces). Returns recent output from the capture file. Use filters to focus on specific content. | |
get_firefox_info | read-only | Get information about the current Firefox instance configuration, including binary path, environment variables, and output file location. | |
close_firefox_session | writes | Ends the browser session. If the server connected to your existing Firefox, this releases the connection and leaves Firefox running. If the server started Firefox itself, this closes it. Call this when the browser task i… | |
install_extension | writes | Install a Firefox extension using WebDriver BiDi webExtension.install command. Supports installing from archive (.xpi/.zip), base64-encoded data, or unpacked directory. | |
uninstall_extension | writes | Uninstall a Firefox extension using WebDriver BiDi webExtension.uninstall command. Requires the extension ID returned by install_extension or obtained from list_extensions. | |
screencast_start | writes | Start recording a screencast (video) of the current page viewport, saving the output to a file in the downloads directory. Returns a screencast id to pass to screencast_stop. Multiple recordings can run at once. | |
screencast_stop | writes | Stop an in-progress screencast recording started with screencast_start and finalize the video file. Returns the path to the saved file. | |
evaluate_script | writes | Run a JS function in the page and return its result. Prefer this for targeted reads (a value, text, computed style, whether an element exists) instead of a full take_snapshot. Use the UID interaction tools for clicking, … |
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