Scan a website for speed problems with Grok

Scanning a site's speed with Grok means asking xAI's chat assistant on grok.com to run an xSpeed Scan through a custom connector, and getting the graded report and its link back in the conversation.

list_sitesget_speed_scanrun_speed_scan

Last updated: October 2026

Example session · Grok

You: Use the xSpeed Scan MCP to check how fast example-florist.com is before we plan the redesign.

run_speed_scan(url: example-florist.com, strategy: both) read-only scan mcp
→ Desktop grade C, mobile grade D. Ranked fixes: page cache (slow first byte), image size, render-blocking font stylesheet. Report link included.

Grok: Desktop C and mobile D. The server builds every page for each visitor, which is the top fix, then heavy images and a font stylesheet that blocks rendering. The redesign can fix the last two; the first is hosting and caching.

You: Is mobile worse only because of images?

Grok: Images are the biggest mobile item, but the slow first byte hurts both runs. The report ranks them by the points each fix would recover.

How Grok handles this

You are in a Grok conversation about something else, a redesign or a marketing plan, and the question of speed comes up. Rather than leave the chat, you ask Grok to scan the site. With the no-account xSpeed Scan MCP added as a custom connector on grok.com, Grok calls run_speed_scan on the public URL and waits for the result, which takes 20 to 60 seconds. It answers with a grade out of 100, the desktop run as the headline and the mobile run beside it, the failing checks with their evidence, and a report link anyone can open.

xAI requires only that a custom connector's server be reachable over the public internet, and the Scan MCP needs no sign-in, so it is the lightest connector you can add. It is also read-only in every tool, which matters in Grok more than in most clients. xAI's connector documentation describes no per-tool approval setting and says Grok can use a connector's tools whenever your question relates to that service, so a connector that cannot change anything is the comfortable one to leave switched on.

For your own sites, add xSpeed Hub as a second custom connector and sign in. Then run_speed_scan takes a site handle, and get_speed_scan reads a site's scan history, so you can ask what shop scored last month without starting a measurement. The Hub classes run_speed_scan as a write tool, because every scan spends a shared speed-test allowance even though it changes nothing on the site. When you re-test after a change, say "fresh", because the same URL within ten minutes returns the existing report.

Set up Grok once

Already connected? Skip to the prompts. Alternatives and troubleshooting are on the Grok guide.

1Put 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.

2Add xSpeed Hub as a custom connector

Go to grok.com/connectors, click New Connector and select Custom. Enter this as the MCP server URL and complete the authentication: approve access on the xSpeed Hub page that opens. Grok then reads the Hub's tools and makes them available in your conversations.

Text

https://app.xspeedcache.com/xspeed/mcp

3Ask a first question

Start a chat and ask something that names xSpeed Hub, so Grok reaches for the connector. A list of your sites with their cache status means the connection works.

Text

Use xSpeed Hub to list my sites and tell me which ones have page caching turned off.

4Add 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 Grok 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.

Text

https://xspeedcache.com/scan/mcp

1 / 4

Full Grok setup, sign-in options and FAQ

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. xAI's connector documentation describes no per-tool approval setting. It says Grok can use a connector's tools whenever your questions relate to that service. xSpeed Hub has no confirmation step of its own, so a purge or a settings change runs as soon as Grok calls it and your connection allows writes. The Hub tells the agent to confirm the target site and to ask once before a write that touches every site, but that is an instruction, not a lock. If you want Grok to read and never change anything, sign in as a Viewer member of the workspace, which only ever gets read access. Otherwise read what Grok says it is about to do before you answer yes.

What do I ask?

Three prompts written for Grok. More for this job are below.

Prompt for Grok

Use the xSpeed Scan MCP to scan [site URL] and tell me the desktop and mobile grades and the biggest fix.

Prompt for Grok

Using xSpeed Hub, what did shop score on its last scan? Do not start a new one.

Prompt for Grok

With the xSpeed Scan MCP, run a fresh mobile-only scan of the same URL and tell me whether the grade changed.

What happens, step by step

An xSpeed Scan grades a site from 0 to 100 using server probes (time to first byte, compression, cache evidence, redirects, platform detection) plus a Lighthouse run, and names the fix for every failing check. An agent can start one two ways. Through xSpeed Hub, run_speed_scan scans a site you have connected. Through the no-account Scan MCP at https://xspeedcache.com/scan/mcp, it scans any public URL and cannot change anything. Either way you get a report link to share.

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.

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.

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.

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.

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.

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 worth keeping

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 Grok

With no approval setting described for connectors, a Hub scan runs as soon as Grok decides your question calls for one, and each one spends the allowance. xSpeed Hub has no confirmation step of its own. If you want Grok to read scan history and never start a Hub scan, sign in to the Hub connector as a Viewer member of the workspace, which refuses run_speed_scan and still allows get_speed_scan; the connection token's Read-only everywhere switch is not part of this setup, because the connector signs in with OAuth. On the Scan MCP the limit is four scans per caller per ten minutes. Reports started through the Scan MCP are public in the scan directory by default, so a scan of a prospect's site leaves a report anyone with the link can open. On Grok Business and Enterprise, a team admin provisions each connector in the cloud console before members can use it.

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.

Prompt

Using xSpeed Hub, what did the shop site score on its last speed scan? Do not start a new one.

Prompt

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.

Prompt

With xSpeed Hub, scan only the mobile view of shop and tell me the grade.

Prompt

I changed the theme this morning. Use xSpeed Hub to run a fresh scan on docs and compare it with the previous report.

Prompt

Use the xSpeed Scan MCP to grade [competitor URL] and tell me what its biggest weaknesses are.

Prompt

The speed scan on shop is still running. Ask xSpeed Hub to check it again and tell me when it finishes.

Frequently asked questions

Yes. Add the xSpeed Scan MCP as a custom connector on grok.com. It needs no sign-in, grades any public URL and cannot change anything. The limit is four scans per caller per ten minutes.

It can. xAI describes no per-tool approval setting for connectors, and the Hub has no confirmation step of its own, so run_speed_scan runs when Grok calls it and spends the shared allowance. A Viewer sign-in refuses it and still lets Grok read your scan history.

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.

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.

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.

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.

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.

Keep going

Scan a site's speed with other agents

More with Grok

Purge the cache Find out why pages are not cached Track PageSpeed scores Raise the PageSpeed score Tune cache settings Warm the cache Set up Redis object cache Manage Cloudflare Manage every site at once

Documentation

From the blog

Scan a site's speed, from Grok.

xSpeed Hub is free and has no site cap. Connect your sites once and ask from the agent you already use.

Open xSpeed Hub Grok setup