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freema

Firefox DevTools MCP

by freema

Server Configuration

Describes the environment variables required to run the server.

NameRequiredDescriptionDefault
START_URLNoOpen this URL on start.
ENABLE_SCRIPTNoEnable the evaluate_script tool. Set to 'true' to enable.
ANDROID_PACKAGENoAndroid app package name. Default is 'org.mozilla.firefox'.
MARIONETTE_PORTNoMarionette port for connect-existing mode. Default is 2828.
CONNECT_EXISTINGNoAttach to an already-running Firefox instead of launching a new one. Set to 'true' to enable.
FIREFOX_HEADLESSNoRun without UI. Set to 'true' to enable headless mode.
ACCEPT_INSECURE_CERTSNoIgnore TLS errors. Set to 'true' to accept insecure certificates.
ENABLE_PRIVILEGED_CONTEXTNoEnable privileged context tools. Set to 'true' to enable. Requires MOZ_REMOTE_ALLOW_SYSTEM_ACCESS=1.

Capabilities

Features and capabilities supported by this server

CapabilityDetails
tools
{}
resources
{}

Tools

Functions exposed to the LLM to take actions

NameDescription
list_pagesA

List open tabs (index, title, URL). Selected tab is marked.

new_pageB

Open new tab at URL. Returns tab index.

navigate_pageB

Navigate selected tab to URL.

select_pageA

Select active tab by index, URL, or title. Index takes precedence.

close_pageC

Close tab by index.

list_console_messagesB

List console messages. Supports filtering by level, time, text, source.

clear_console_messagesA

Clear collected console messages.

list_network_requestsC

List network requests. Returns IDs for get_network_request.

get_network_requestA

Get request details by ID. URL lookup as fallback.

take_snapshotA

Capture DOM snapshot with stable UIDs. Retake after navigation.

resolve_uid_to_selectorB

Resolve UID to CSS selector. Fails if stale.

clear_snapshotB

Clear snapshot cache. Usually not needed.

click_by_uidB

Click element by UID. Set dblClick for double-click.

hover_by_uidC

Hover over element by UID.

fill_by_uidC

Fill text input/textarea by UID.

drag_by_uid_to_uidC

Drag element to another (HTML5 drag events).

fill_form_by_uidC

Fill multiple form fields at once.

upload_file_by_uidB

Upload file to file input by UID.

screenshot_pageB

Capture page screenshot as base64 PNG.

screenshot_by_uidB

Capture element screenshot by UID as base64 PNG.

accept_dialogA

Accept browser dialog. Provide promptText for prompts.

dismiss_dialogA

Dismiss browser dialog.

navigate_historyA

Navigate history back/forward. UIDs become stale.

set_viewport_sizeB

Set viewport dimensions in pixels.

get_firefox_outputC

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_infoA

Get information about the current Firefox instance configuration, including binary path, environment variables, and output file location.

restart_firefoxA

Restart Firefox with different configuration. Allows changing binary path, environment variables, and other options. All current tabs will be closed.

install_extensionB

Install a Firefox extension using WebDriver BiDi webExtension.install command. Supports installing from archive (.xpi/.zip), base64-encoded data, or unpacked directory.

uninstall_extensionA

Uninstall a Firefox extension using WebDriver BiDi webExtension.uninstall command. Requires the extension ID returned by install_extension or obtained from list_extensions.

Prompts

Interactive templates invoked by user choice

NameDescription

No prompts

Resources

Contextual data attached and managed by the client

NameDescription

No resources

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