FSB vs PWA Debug Layer
A side-by-side look at the FSB and PWA Debug Layer MCP servers: transport, auth, tools, quality signals, and the config to install either one in Claude, Cursor, Windsurf or VS Code.
Verdict: choose FSB for browser automation work as a local process; choose PWA Debug Layer for browser automation as a local process. You can also run both side by side in one mcpServers block.
Which MCP server should you choose?
Choose FSB when
- You need dedicated capabilities in the Browser Automation domain.
- You prefer a local stdio subprocess transport.
- Its auth model fits you: No auth required.
- You want tools like
start_visual_session, end_visual_session, trigger.
Choose PWA Debug Layer when
- You need dedicated capabilities in the Browser Automation domain.
- You prefer a local stdio subprocess transport.
- You want tools like
click, close_page, drag.
Feature & specification comparison
Rows where the two servers differ are marked.
| Spec | ||
|---|---|---|
| Category | Browser Automation | Browser Automation |
| Quality signal | 64/100 · Good | 59/100 · Good |
| Install command | Confirmed | Confirmed |
| Transport | Local subprocess (stdio) | Local subprocess (stdio) |
| Auth | No auth required | Not declared |
| Pricing | Free | Not declared |
| Required env vars | None listed | None listed |
| Verified owner | Community listing | Community listing |
| GitHub stars | 202 | 0 |
| Directory activity | 0 views 0 installs 0 upvotes | 2 views 0 installs 0 upvotes |
| Tools | 72 | 32 |
| Full listing | View FSB | View PWA Debug Layer |
Tools & capabilities
FSB tools 72
start_visual_session[REMOVED in v0.9.0] This tool was removed in fsb-mcp-server v0.9.0 (FSB v0.9.62 implicit visual-session contract). Calling it returns the typed TOOL_REMOVED error with a migration recipe pointer. The visual session is now implicit on every action tool call via the required visual_reason + client field bundle -- there is no longer a separate start call. See CHANGELOG.md#v0.9.0 and the Visual Session Lifecycle section of mcp/README.md for the migration recipe.end_visual_session[REMOVED in v0.9.0] This tool was removed in fsb-mcp-server v0.9.0 (FSB v0.9.62 implicit visual-session contract). Calling it returns the typed TOOL_REMOVED error with a migration recipe pointer. The visual session now clears either automatically after 60 seconds of silence (sliding window) or immediately when an action tool is called with is_final: true -- there is no longer a separate end call. See CHANGELOG.md#v0.9.0 and the Visual Session Lifecycle section of mcp/README.md for the migration recipe.triggerArm a reactive DOM trigger on one selector. Use this when the user wants to watch an element until it changes, crosses a threshold, equals or matches a value, or contains text. The watch is owned by the background trigger runtime and persisted across service-worker eviction. Pass one selector and one condition object; runtime validation checks the nested condition details before arming. Use stop_trigger to cancel, get_trigger_status to inspect one watcher, and list_triggers to enumerate watchers.stop_triggerCancel a trigger by id. This is cancellation-critical and bypass-class: it must be callable promptly even if a trigger or another mutation is pending. Missing or already terminal triggers are handled idempotently by the background trigger runtime.get_trigger_statusRead the persisted status for one trigger by id. Returns storage-of-truth trigger state including status, watch mode, condition, target tab, owner, current value, timing, and attention details when available.list_triggersList persisted trigger snapshots. By default, returns active and attention-state watchers; include_terminal can include fired and stopped triggers for audit or cleanup workflows.execute_jsRun JavaScript directly in the active page. PRIMARY INTERACTION TOOL: try execute_js FIRST for clicks, scrolls, reads, attribute lookups, and most other DOM work -- it bypasses overlay/obscured-element issues, viewport constraints, and CDP timeouts that block native click/scroll. Typical patterns: `return document.querySelector('#add-to-cart-button').click(), true;` for clicks; `return Array.from(document.querySelectorAll('a')).map(a=>a.href);` for extraction; `window.scrollTo(0, document.body.scrollHeight); return true;` for scroll. After a JS click, verify with read_page or get_page_snapshot (a true click should produce observable DOM change). FALLBACK TO NATIVE TOOLS WHEN: (1) JS click reports success but the page state did not change (framework swallowed the synthetic event -- use native click which fires real CDP events that React/Angular/Vue listen to); (2) typing into controlled text inputs (use native `type` so React onChange fires correctly -- `element.value = ...` will NOT update component state); (3) real drag operations on react-beautiful-dnd / Sortable.js / Trello-style widgets (use drag_drop / drag for real pointer events); (4) form submission that depends on validated input state (use native click on submit). Code runs as a function body -- use `return` to send values back (results are stringified). Async work: Promises are not awaited, so fire-and-forget then poll on `window.__yourKey`. Related: read_page (verify result), get_dom_snapshot (debug after JS click), click / type / drag_drop (fallbacks when JS doesn't take effect). Multi-agent: agent-scoped tabs; cross-agent reject with TAB_NOT_OWNED; cap configurable (default 8, 1-64). Pass tab_id only when this agent owns multiple tabs; auto-resolves otherwise. RETURNS change_report: when this tool runs, the response includes a `change_report` field with a compact diff of what the action mutated (URL, dialogs_opened, nodes_added, nodes_removed, attrs_changed, inputs_changed, focus_shift). Use this to learn the consequence without calling read_page next. If the report exceeds the size cap, `change_report.truncated:true` and `change_report_hint` are set; call read_page for the full state.navigateOpen a URL in the active browser tab. Returns the final URL after any redirects. When to use: as the first step to reach a target website. Related: read_page (read content after navigating), list_tabs (see what tabs are already open). Multi-agent: agent-scoped tabs; cross-agent reject with TAB_NOT_OWNED; cap configurable (default 8, 1-64). Pass tab_id only when this agent owns multiple tabs; auto-resolves otherwise. RETURNS change_report: when this tool runs, the response includes a `change_report` field with a compact diff of what the action mutated (URL, dialogs_opened, nodes_added, nodes_removed, attrs_changed, inputs_changed, focus_shift). Use this to learn the consequence without calling read_page next. If the report exceeds the size cap, `change_report.truncated:true` and `change_report_hint` are set; call read_page for the full state.searchSearch for content on the current site or web. When to use: to find content on the current site or web. Automatically detects the site's search input (Amazon, YouTube, GitHub, etc.) via DOM heuristics -- only falls back to Google when no site search exists. Returns search results status. Related: read_page (read search results after searching), click (click a specific search result). Multi-agent: agent-scoped tabs; cross-agent reject with TAB_NOT_OWNED; cap configurable (default 8, 1-64). Pass tab_id only when this agent owns multiple tabs; auto-resolves otherwise.go_backNavigate back one page in browser history. Returns the new URL. When to use: to return to the previous page after following a link or navigating away. Related: go_forward (undo a go_back), navigate (go to a specific URL instead). Multi-agent: agent-scoped tabs; cross-agent reject with TAB_NOT_OWNED; cap configurable (default 8, 1-64). Pass tab_id only when this agent owns multiple tabs; auto-resolves otherwise. RETURNS change_report: when this tool runs, the response includes a `change_report` field with a compact diff of what the action mutated (URL, dialogs_opened, nodes_added, nodes_removed, attrs_changed, inputs_changed, focus_shift). Use this to learn the consequence without calling read_page next. If the report exceeds the size cap, `change_report.truncated:true` and `change_report_hint` are set; call read_page for the full state.go_forwardNavigate forward one page in browser history. Returns the new URL. When to use: after using go_back, to move forward again. Related: go_back (go back in history), navigate (go to a specific URL instead). Multi-agent: agent-scoped tabs; cross-agent reject with TAB_NOT_OWNED; cap configurable (default 8, 1-64). Pass tab_id only when this agent owns multiple tabs; auto-resolves otherwise. RETURNS change_report: when this tool runs, the response includes a `change_report` field with a compact diff of what the action mutated (URL, dialogs_opened, nodes_added, nodes_removed, attrs_changed, inputs_changed, focus_shift). Use this to learn the consequence without calling read_page next. If the report exceeds the size cap, `change_report.truncated:true` and `change_report_hint` are set; call read_page for the full state.refreshReload the current page. Returns the refreshed URL. When to use: when page content may be stale, after errors, or to reset page state. Related: navigate (go to a different URL), wait_for_stable (wait for page to settle after refresh). Multi-agent: agent-scoped tabs; cross-agent reject with TAB_NOT_OWNED; cap configurable (default 8, 1-64). Pass tab_id only when this agent owns multiple tabs; auto-resolves otherwise. RETURNS change_report: when this tool runs, the response includes a `change_report` field with a compact diff of what the action mutated (URL, dialogs_opened, nodes_added, nodes_removed, attrs_changed, inputs_changed, focus_shift). Use this to learn the consequence without calling read_page next. If the report exceeds the size cap, `change_report.truncated:true` and `change_report_hint` are set; call read_page for the full state.- +60 more on the listing page
PWA Debug Layer tools 32
clickClicks on the provided elementclose_pageCloses the page by its index. The last open page cannot be closed.dragDrag an element onto another elementemulateEmulates various features on the target page. Each call replaces all emulation settings (except extraHttpHeaders), so pass all desired settings in a single call.evaluate_scriptEvaluate JavaScript inside the target page. The source can be provided inline or loaded from a local file. Returns the response as JSON, so returned values have to be JSON-serializable.fillType text into an input, text area or select an option from a <select> element.fill_formFill out multiple form elements (inputs, selects, checkboxes, radios) at once. ALWAYS prefer this tool over multiple individual 'fill' or 'click' calls when interacting with forms. It is significantly faster, more reliable, and reduces turn count. Example: Fill username, password, and check "Remember Me" in one call.get_console_messageGets a console message by its ID. You can get all messages by calling list_console_messages.get_css_stylesRetrieve matched CSS rules, inline styles (element.style), inherited styles, custom properties, and cascade wrappers (@layer, @media, @container, @scope) for an element identified by its UID. Rules are ordered from highest to lowest cascade precedence and include source line numbers (e.g. index:196). Active (winning) declarations have no prefix tag, while (losing) overridden declarations are prefixed with [overloaded]. Treat the output as authoritative and complete. Results are paginated (10 rules per page by default); use pageIdx to page through the remaining rules. Requires a UID from take_snapshot.get_network_requestGets a network request by an optional reqid, if omitted returns the currently selected request in the DevTools Network panel. Useful for inspecting request headers (including 'Cookie') and response headers (including 'Set-Cookie' and directives).handle_dialogIf a browser dialog was opened, use this command to handle ithoverHover over the provided element- +20 more on the listing page
Ready-to-paste client configs
Paste either block (or both) into your client config, e.g. claude_desktop_config.json or ~/.cursor/mcp.json. We only show a config when the install command is confirmed.
FSB
{
"mcpServers": {
"fullselfbrowsing-fsb": {
"command": "npx",
"args": [
"-y",
"fsb-mcp-server@latest"
]
}
}
}
PWA Debug Layer
{
"mcpServers": {
"pwa-debug-layer": {
"command": "npx",
"args": [
"-y",
"chrome-devtools-mcp@latest"
]
}
}
}
Frequently asked questions
FSB is categorized under Browser Automation and uses a local stdio subprocess. PWA Debug Layer belongs to Browser Automation and uses a local stdio subprocess. Pick FSB for browser automation work and PWA Debug Layer for browser automation.
Copy the mcpServers block from the config section on this page into your client's config (for example claude_desktop_config.json or ~/.cursor/mcp.json), then fully restart the client.
FSB is listed as free. Auth: no auth required. PWA Debug Layer has no declared pricing — check the project's own site. If a server needs environment variables such as API keys, define them under the env key in your client's MCP config.
Yes. MCP clients support multiple servers: add fullselfbrowsing-fsb and pwa-debug-layer as separate keys in the same mcpServers object, and your assistant will call tools from either one.
On AllMCPs, FSB has a quality signal of 64/100 (Good) with 0 views, 0 installs and 202 GitHub stars. PWA Debug Layer has 59/100 (Good) with 2 views, 0 installs and 0 GitHub stars.
