# Scan a website for speed problems with Antigravity

> Scanning a site's speed with Antigravity means giving one of its agents the URL and having it run an xSpeed Scan, then report the grades, the ranked fixes and the shareable link.

Page: https://xspeedcache.com/agent/antigravity/speed-scan/
Last updated: October 2026

Antigravity is built around handing an agent a task and checking the result, and a scan is a good small task. You say which site to scan and what you want back. The agent calls run_speed_scan through xSpeed Hub, or through the no-account Scan MCP if the site is not in your Hub, and returns a grade out of 100. The desktop run is the headline, the mobile run is graded alongside, and each failing check comes with the evidence and the fix.

It works best when the ask is specific about the output. Ask for the two grades, the three failing checks that recover the most points, and the report link. Then ask for one follow-up that depends on the result, such as listing which of those checks you can fix from your code and which need a plugin setting. The agent has the structured result in hand, so the follow-up costs no second scan.

To see movement over time, ask it to read the scan history with get_speed_scan before it measures anything. That call spends nothing, and the history shows which device was graded on every row, so an old mobile-graded report is not mistaken for a desktop one. Keep the report links from each run in the task notes, because they stay valid and let you or a teammate reopen exactly what the agent saw.

## Set up Antigravity once

### 1. Put your sites in xSpeed Hub

Sign in at app.xspeedcache.com with Google or email; the Hub is free and has no site cap. Then connect each WordPress site from its own dashboard: click Connect Hub in the xSpeed Cache top bar, then Connect via xSpeed Hub. Each site needs the free xSpeed Cache plugin.

### 2. Add xSpeed Hub to mcp_config.json

Antigravity reads ~/.gemini/config/mcp_config.json for every project, or .agents/mcp_config.json inside one workspace. In the IDE, open the ... menu at the top of the agent side panel, choose MCP Servers, then Manage MCP Servers and View raw config. Remote servers must use the serverUrl field; the older url and httpUrl fields are not supported.

File: `~/.gemini/config/mcp_config.json`

```json
{
  "mcpServers": {
    "xspeedhub": {
      "serverUrl": "https://app.xspeedcache.com/xspeed/mcp"
    }
  }
}
```

### 3. Authenticate

Open Agent settings with Cmd+, on macOS or Ctrl+, on Windows and Linux, go to the Customizations tab and click Authenticate next to xspeedhub. Sign in to xSpeed Hub in the browser and approve access, copy the authorization code the page shows, paste it into the settings panel and click Submit. Antigravity keeps the credentials it receives and refreshes them. In the CLI, type /mcp to open the MCP manager and check the server status.

```
Settings → Customizations → Authenticate
```

### 4. Add the xSpeed Scan MCP for sites you do not run

Prompts that scan a public URL use the xSpeed Scan MCP, a separate server from the Hub. Add it to Antigravity the same way as the Hub above, as a second server (xspeedscan, for example) with the URL https://xspeedcache.com/scan/mcp, and leave out any sign-in setting, such as an OAuth or auth option or an Authorization header, because the Scan MCP needs no account, token or sign-in. On a plan that allows one custom connector, add whichever server the prompts you use need.

```
https://xspeedcache.com/scan/mcp
```

Full setup: https://xspeedcache.com/agent/antigravity/

### Before you send a prompt that changes something

Reads change nothing on your sites, though contact_support emails xSpeed support. Writes run once your connection allows them, so your client's approval prompt and a read-only connection (the token's Read-only everywhere switch, or a Viewer sign-in) are the gates that matter. Antigravity runs unconfigured MCP tools in Ask mode, so each call waits for your approval in a card before it executes. Allow rules such as mcp(xspeedhub/get_cache_status) or mcp(xspeedhub/*) let calls through without a prompt, Ask and Deny rules take precedence over Allow, and the Turbo permission preset allows MCP and web actions without asking. When you approve a card you can also edit its target to widen the grant. With Turbo or a broad allow rule, a write reaches the Hub as soon as your connection allows writes. xSpeed Hub has no confirmation step of its own.

## Prompts

- Use xSpeed Hub to scan the site, then give me two lines: the desktop and mobile grades and the biggest fix, plus the report link.
- With xSpeed Hub, read the scan history for shop and summarize the trend in one sentence.
- Use the xSpeed Scan MCP to scan the competitor URL and tell me which of its checks are better than ours.

## Example session

```
You: Use xSpeed Hub to scan shop and give me the grades and the biggest fix.
  → run_speed_scan(site: shop, strategy: both) [uses quota]: Desktop grade B, mobile grade C. Failing checks, ranked: image optimization (top on mobile), render-blocking stylesheet, page cache. Report link included.
Agent: Desktop B, mobile C. The biggest fix is image optimization, which is the top failing check on mobile. The report link is attached.
You: Which of those checks can be fixed in our code?
Agent: Image sizes and stylesheet loading are usually set in the theme; I can check the code and draft the changes. The cache check is a plugin setting.
```

## How it works

1. **Check what the site already scored**: get_speed_scan without a scan id returns the site's scan history, newest first, plus a summary of the latest report. It starts nothing and spends nothing, so the Hub tells the agent to read it first when you ask what a site scored.
2. **Start a scan**: run_speed_scan runs the full scan on a site you connected to the Hub. strategy is both (the default), desktop or mobile; one device alone costs half the engine's quota. The scan takes 20 to 60 seconds. The Hub waits about 50 seconds and, if the scan is still running, hands back a scan id.
3. **Poll if it is still running**: Call get_speed_scan with scan_id. While the scan runs it returns the running status and a note to ask again in about 20 seconds. The report page is live from the start and refreshes itself.
4. **Read the result**: The summary carries the grade, the four dimension scores, what was measured and the top fixes ranked by points recoverable, each with the xSpeed feature that fixes it. The headline grade is the desktop run. The mobile run is graded alongside it, so the agent should mention both when they differ.
5. **Scan a site you do not run**: For any other public URL, the agent uses the Scan MCP at https://xspeedcache.com/scan/mcp. There is no account and no sign-in. It takes a url, returns the same graded report and a link at xspeedcache.com/scan/r/<id>, and is limited to 4 scans per caller per 10 minutes.
6. **Fix, wait, re-scan**: After a change, wait several minutes and scan again with fresh: true. Without it, the scan service reuses any report from the last 10 minutes and the agent will show you the old number.

## Reference

| | |
| --- | --- |
| Hub route | run_speed_scan, then get_speed_scan with scan_id; only for sites connected to your Hub |
| Scan MCP route | https://xspeedcache.com/scan/mcp, no account, 5 tools, read-only, any public URL |
| Scan MCP limit | 4 scans per caller per 10 minutes |
| Why run_speed_scan is a write | It spends a shared scan allowance and stores a report; it changes nothing on the site |
| Read-only Hub connection | run_speed_scan is refused; get_speed_scan still works. Applies to the connection token with Read-only everywhere on and to a Viewer sign-in; an OAuth sign-in gets the scopes the client asks for |
| Duration | 20 to 60 seconds; the Hub waits about 50 seconds, then returns a scan id |
| Poll argument | scan_id on the Hub tool, scanId on the Scan MCP tool |
| strategy | both (default), desktop or mobile; one device costs half the quota and becomes the headline |
| fresh | true forces a new measurement; otherwise a report from the last 10 minutes is reused |
| Report link | xspeedcache.com/scan/r/<id>; add .md for a Markdown twin an agent can read |
| Report visibility | Hub scans are filed unlisted; Scan MCP scans are public in the scan directory by default |

## Rules

- Read before you spend. Ask for the scan history first; start a new scan only when you want a fresh measurement or something changed.
- A report link is not private. An unlisted report is kept out of the scan directory and search, but anyone with the URL can open it. A scan started through the Scan MCP is public by default.
- run_speed_scan changes nothing on your site, but the Hub classes it a write, so a read-only connection (the connection token with Read-only everywhere on, or a Viewer sign-in) refuses it and your client may prompt for it. Use get_speed_scan, or the Scan MCP for a public URL, when you want a strictly read-only route.
- Compare like with like. A scan that lost its Lighthouse run is marked partial and is not comparable with a full one, and the lab grade is not the same as real-visitor Core Web Vitals, which the report shows separately.
- A scan cannot reach private, local or password-protected sites, and a site behind a bot challenge returns a report that says its server checks were not measured.

## Good to know with Antigravity

Antigravity runs unconfigured MCP tools in Ask mode, so each call waits for your approval in a card. The Turbo permission preset allows MCP actions without asking, and an allow rule such as mcp(xspeedhub/*) does the same for the whole Hub. Then run_speed_scan starts as soon as the agent decides to, and the Hub classes it as a write tool because each scan spends the shared speed-test allowance. Allow get_speed_scan on its own and add an Ask rule for run_speed_scan, since Ask and Deny rules take precedence over Allow. A read-only Hub connection (the connection token with Read-only everywhere on, or a Viewer sign-in) refuses run_speed_scan whatever the preset. For an agent that scans with no such risk, point it at the no-account Scan MCP, which is read-only and limited to four scans per caller per ten minutes.

## More prompts for this job

Prompts about your own sites work in any client connected to xSpeed Hub. A prompt that scans a site you do not run, or names the scan server, needs the xSpeed Scan MCP from the setup above.

- Using xSpeed Hub, what did the shop site score on its last speed scan? Do not start a new one.
- Use xSpeed Hub to run a speed scan on blog and give me the three fixes that recover the most points, plus the report link.
- With xSpeed Hub, scan only the mobile view of shop and tell me the grade.
- I changed the theme this morning. Use xSpeed Hub to run a fresh scan on docs and compare it with the previous report.
- Use the xSpeed Scan MCP to grade [competitor URL] and tell me what its biggest weaknesses are.
- The speed scan on shop is still running. Ask xSpeed Hub to check it again and tell me when it finishes.

## Frequently asked questions

### Does Antigravity ask me before an agent runs a scan?

By default it does. Unconfigured MCP tools run in Ask mode and wait for your approval, but the Turbo preset or an allow rule removes that prompt. The firm limit is on the xSpeed side: a Hub connection token set to Read-only everywhere refuses run_speed_scan, and the Scan MCP is read-only altogether.

### Can the agent compare today's scan with an older one?

Yes. Ask it to call get_speed_scan for the site first, which reads past reports without starting a scan, then run a fresh scan. It should compare the same device, since reports before the desktop headline change were graded on mobile.

### What is the difference between run_speed_scan and run_speed_test?

run_speed_scan runs the full xSpeed Scan: server probes plus Lighthouse, a 0 to 100 grade across four dimensions, the fix for every failing check and a shareable report link. run_speed_test returns a raw PageSpeed Insights score with Core Web Vitals and no graded report.

### Can an agent scan a site that is not in my Hub?

Yes, through the xSpeed Scan MCP at https://xspeedcache.com/scan/mcp. It needs no account and no sign-in, accepts any public URL and is read-only. The Hub route only scans sites you connected to your own workspace.

### How many scans can I run?

The Scan MCP allows 4 scans per caller per 10 minutes. Scanning the same URL again within 10 minutes returns the existing report unless the agent passes fresh: true. A Hub scan spends a shared allowance of the scan service, which is why the Hub treats it as a write tool.

### Is my scan report public?

Reports started from the Hub are filed as unlisted, which keeps them out of the public scan directory and search results, but the link itself still opens for anyone who has it. Reports started through the Scan MCP are public by default.

### Which score does the scan headline show, desktop or mobile?

The headline grade is the desktop run, because it is the one you can reproduce in your own browser. The mobile run is graded on the same rubric and returned alongside it. Google ranks on mobile, so when the two differ the agent should tell you both.

## Scan a site's speed with other agents

[Claude Code](https://xspeedcache.com/agent/claude-code/speed-scan/) · [Claude](https://xspeedcache.com/agent/claude/speed-scan/) · [Claude Cowork](https://xspeedcache.com/agent/claude-cowork/speed-scan/) · [ChatGPT](https://xspeedcache.com/agent/chatgpt/speed-scan/) · [Codex](https://xspeedcache.com/agent/codex/speed-scan/) · [Cursor](https://xspeedcache.com/agent/cursor/speed-scan/) · [GitHub Copilot in VS Code](https://xspeedcache.com/agent/github-copilot/speed-scan/) · [Windsurf](https://xspeedcache.com/agent/windsurf/speed-scan/) · [Gemini CLI](https://xspeedcache.com/agent/gemini-cli/speed-scan/) · [Zed](https://xspeedcache.com/agent/zed/speed-scan/) · [Kiro](https://xspeedcache.com/agent/kiro/speed-scan/) · [OpenCode](https://xspeedcache.com/agent/opencode/speed-scan/) · [OpenClaw](https://xspeedcache.com/agent/openclaw/speed-scan/) · [Hermes Agent](https://xspeedcache.com/agent/hermes-agent/speed-scan/) · [Grok Build](https://xspeedcache.com/agent/grok-build/speed-scan/) · [ChatGPT dots](https://xspeedcache.com/agent/chatgpt-dots/speed-scan/) · [Grok](https://xspeedcache.com/agent/grok/speed-scan/) · [Grok Bot](https://xspeedcache.com/agent/grok-bot/speed-scan/) · [Muse](https://xspeedcache.com/agent/muse/speed-scan/) · [Manus](https://xspeedcache.com/agent/manus/speed-scan/) · [Kimi Code](https://xspeedcache.com/agent/kimi/speed-scan/) · [Paperclip](https://xspeedcache.com/agent/paperclip/speed-scan/) · [NanoClaw](https://xspeedcache.com/agent/nanoclaw/speed-scan/)

## More with Antigravity

- [Purge the WordPress cache with Antigravity](https://xspeedcache.com/agent/antigravity/purge-cache/)
- [Find out why WordPress pages are not cached with Antigravity](https://xspeedcache.com/agent/antigravity/troubleshoot-cache/)
- [Run and track PageSpeed tests with Antigravity](https://xspeedcache.com/agent/antigravity/pagespeed-tests/)
- [Raise a WordPress site's PageSpeed score with Antigravity](https://xspeedcache.com/agent/antigravity/optimize-site/)
- [Tune WordPress cache settings with Antigravity](https://xspeedcache.com/agent/antigravity/cache-settings/)
- [Warm the WordPress cache with Antigravity](https://xspeedcache.com/agent/antigravity/preload-cache/)
- [Set up the Redis object cache with Antigravity](https://xspeedcache.com/agent/antigravity/object-cache/)
- [Manage Cloudflare caching with Antigravity](https://xspeedcache.com/agent/antigravity/cloudflare/)
- [Manage every WordPress site at once with Antigravity](https://xspeedcache.com/agent/antigravity/fleet/)

## Documentation

- xSpeed Scan: free website speed test: https://xspeedcache.com/docs/speed-scan/
- xSpeed Scan MCP: speed-test any site from your AI assistant: https://xspeedcache.com/docs/scan-mcp/
- How to run a full site scan: https://xspeedcache.com/docs/scan/
- Running speed tests in xSpeed Hub: https://xspeedcache.com/docs/hub-speed-tests-and-notifications/