appsmith-mcp

An MCP server that lets an AI agent control Appsmith — building and editing apps (pages, widgets, queries, datasources, JS objects, themes) by driving the real editor in the browser. It attaches to a running Firefox over the WebDriver BiDi protocol and reads/dispatches the editor's Redux store, so an agent can operate Appsmith the same way a person would.

How it works

Appsmith has no public API for editing apps — the builder lives entirely in the browser. This server drives that builder in place: it attaches to a running Firefox over WebDriver BiDi, finds Appsmith's Redux store on the open editor page, and runs predefined JavaScript snippets against it.

Each tool is one such snippet. Reads pull straight from Redux state; writes dispatch the same actions the editor UI fires when you click — so creating a widget, wiring a query, or editing a custom widget's source is the programmatic equivalent of doing it by hand, and changes render live and save to the Appsmith backend.

The tools cover the full editor surface but lean toward custom widgets — self-contained HTML/CSS/JS components — since AI is generally better at building a UI as code than by arranging Appsmith's native widgets on a visual grid.

Related MCP server: harness-fe

Prerequisites

• Firefox — the server attaches to a running instance.

• Python 3.10+ and uv or pip.

• A reachable Appsmith instance you can log into.

Install

uv:

uv sync

pip:

python3 -m venv .venv
source .venv/bin/activate
pip install -e .

Launch Firefox with remote debugging

./launch.sh

This kills any running Firefox and reopens it with the BiDi port enabled (works on macOS, Linux, and Windows via Git Bash). Log into Appsmith and navigate to an app's editor page (.../edit) in that window. The server re-bootstraps on the next tool call after any navigation.

Register with Claude Code

claude mcp add --scope user appsmith /path/to/appsmith-mcp/.venv/bin/appsmith-mcp

After launching/relaunching Firefox, reconnect the server with /mcp so it re-attaches.

Tools

App & workspace

• list_workspaces — List workspaces (id and name).

• list_apps — List all applications across workspaces, with editor URLs.

• create_app — Create a new application.

• update_app — Update the current app's metadata and settings (name, navigation, theme, layout).

• delete_app — Delete an application by id.

• get_state_summary — Counts of widgets, datasources, and queries in the current app.

• dump_state — Dump the current app's pages and widget tree (optionally full detail).

• get_logs — Return log/error metadata (no message text).

Pages

• list_pages — List the app's pages, flags, and which is active.

• create_pages — Create one or more blank pages.

• delete_pages — Delete one or more pages.

• switch_page — Switch the editor to another page.

Custom widgets

• create_custom_widget — Create a self-contained HTML/CSS/JS widget (the primary entrypoint).

• get_custom_widget — Return a custom widget's source, model, events, name, and position.

• update_custom_widget — Update its model, name, events, triggers, height mode, or position.

• delete_custom_widget — Delete a custom widget by id.

• patch_widget_code — Make targeted edits to a custom widget's source without rewriting it.

Widgets (native)

• add_widgets — Add one or more native widgets.

• update_widgets — Apply property updates to one or more widgets.

• delete_widgets — Delete one or more widgets (cascades children).

• set_widget_bounds — Move and/or resize widgets.

• rename_widgets — Rename widgets.

• reparent_widgets — Move widgets to a new parent canvas.

• clear_canvas — Delete every widget on the page.

• get_widget — Return a widget's full Redux record.

• check_layout — Diagnose layout/overflow issues across the page.

• list_widget_types — List widget types with a known property schema.

• get_widget_schema — Return a widget type's property schema (controls, validation, defaults).

• manage_table_columns — Add, remove, or reorder columns on a table widget.

• manage_tabs — Add, remove, or reorder tabs on a tabs widget.

JS objects

• list_js_objects — List JS objects with their declared function names.

• get_js_objects — Return full source of JS objects (bodies, functions, variables).

• create_js_objects — Create one or more JS objects.

• update_js_objects — Replace the source of one or more JS objects.

• delete_js_objects — Delete one or more JS objects.

• patch_js_objects — Make targeted edits to JS object bodies without rewriting them.

• execute_js_functions — Run JS object functions and return their results.

Queries

• list_queries — List the app's queries (datasource actions).

• create_queries — Create one or more queries bound to datasources.

• update_queries — Update one or more queries.

• delete_queries — Delete one or more queries.

• execute_queries — Run queries by id and return their responses.

Datasources

• list_datasources — List datasources in the current workspace.

• create_datasources — Create one or more datasources.

• update_datasources — Update one or more datasources.

• delete_datasources — Delete one or more datasources.

• list_plugins — List available plugins (REST, Postgres, MongoDB, etc.).

Themes

• list_themes — List built-in and saved custom themes.

• get_current_theme — Return the active theme and its color/font/radius/shadow values.

• set_theme — Switch the app to a theme by id.

• update_theme — Patch the current theme's properties.

• save_custom_theme — Save the current theme as a named custom theme.

• delete_custom_themes — Delete saved custom themes.

Browser & navigation

• get_url — Return the URL loaded in the attached Firefox tab.

• navigate — Navigate the tab to a URL.

• refresh_page — Reload the tab and wait for it to finish.

• run_command — Evaluate arbitrary JS in the tab and return the result.

⚠️ run_command evaluates arbitrary JavaScript in the attached browser tab with full access to the Redux store and the page — it can read or modify anything in the live session, bypassing the safety constraints of the other tools. It's an escape hatch for exploring state and discovering action shapes; use it deliberately.

License

MIT