Scan a website for speed problems with Codex

Scanning a site's speed with Codex means asking it, in the terminal session where it edits your code, to run an xSpeed Scan on the URL it just changed and read the graded result.

list_sitesget_speed_scanrun_speed_scan

Last updated: October 2026

Example session · Codex

You: Use xSpeed Hub to compare shop before and after the template change. Scan it fresh.

get_speed_scan(site: shop) read-only
→ Previous report: desktop grade B, mobile grade C

run_speed_scan(site: shop, fresh: true, strategy: both) uses quota
→ Desktop grade B, mobile grade B. Remaining failing check: unoptimized images on the homepage. Report link included.

Codex: Desktop held at B and mobile moved from C to B. The remaining failing check is unoptimized images on the homepage. Report link attached for the PR description.

How Codex handles this

The useful moment is the end of a task. Codex has changed a theme template, a caching setting or a plugin, and before you accept the work you want a measurement. You ask it to scan the site. If the site is in xSpeed Hub, Codex calls run_speed_scan with the site handle, and with get_speed_scan it first reads what the site scored before, so the comparison is against a real earlier report and not a guess.

The scan returns server probes and a Lighthouse run graded out of 100 on one rubric. The desktop run is the headline and the mobile run is graded beside it. The failing checks come ranked by points recovered, with the xSpeed feature that fixes each. Codex can then act on the list in your repository, or in the plugin settings if you have connected the site, and re-scan with a fresh run to prove the difference.

If the page is not in your Hub, such as a client's live site or a staging page, the no-account Scan MCP grades any public URL. It is read-only, so Codex can use it freely, within four scans per caller per ten minutes. Paste the report link into the pull request or the commit notes, so the reviewer can open the same evidence Codex read and judge the change for themselves.

Set up Codex once

Already connected? Skip to the prompts. Alternatives and troubleshooting are on the Codex 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 and sign in

Add the server with its URL, then log in. The login opens an xSpeed Hub page in your browser; approve access there. There is no token to paste, and Codex keeps the credentials it receives. Start Codex and type /mcp to see the server.

Terminal

codex mcp add xspeedhub --url https://app.xspeedcache.com/xspeed/mcp
codex mcp login xspeedhub

3Keep the Hub's tools on a prompt

Open ~/.codex/config.toml. Set the server to prompt for every tool, then let one read tool run without a question. The tool timeout defaults to 60 seconds, and a PageSpeed test can take up to about two minutes, so raise it.

~/.codex/config.toml

[mcp_servers.xspeedhub]
url = "https://app.xspeedcache.com/xspeed/mcp"
default_tools_approval_mode = "prompt"
tool_timeout_sec = 150

[mcp_servers.xspeedhub.tools.get_cache_status]
approval_mode = "approve"

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 Codex 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 Codex 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. Codex has two layers for shell work: the sandbox mode limits what commands can touch, and the approval policy sets when Codex stops to ask. MCP tools have their own settings. Each server takes default_tools_approval_mode (auto, prompt, writes or approve) and each tool can override it with approval_mode. Codex also asks about MCP calls that advertise side effects or a destructive annotation, but xSpeed Hub's tool definitions do not declare either, so do not rely on that default for the Hub; set the server to prompt. approval_policy never, --yolo and an auto_review reviewer take the human out of the loop. xSpeed Hub has no confirmation step of its own, so an approved or auto-approved write runs as soon as your connection allows writes.

What do I ask?

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

Prompt for Codex

Use xSpeed Hub to read the last scan for shop, make the change we discussed, then run a fresh scan and tell me which grades moved.

Prompt for Codex

With the xSpeed Scan MCP, scan the public staging URL and list the failing checks as a TODO for this branch.

Prompt for Codex

Ask xSpeed Hub for a mobile-only scan of the homepage and report the top three checks by points recovered.

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 Codex

A preview or staging URL has to be reachable from the public internet, because the scan runs from the xSpeed servers and not from your machine. A page behind a password, a VPN or a local address cannot be scanned, and Codex will get an error or an unusable report. Codex only prompts by default for MCP calls that advertise side effects, and the Hub's tools declare none, so set the Hub server to prompt and let get_speed_scan through with a per-tool override. approval_policy never, --yolo and an auto-approving reviewer remove the prompt, and then run_speed_scan, a write-classed tool that spends the shared allowance, runs unasked. The tool timeout defaults to 60 seconds and the Hub waits about 50, so raise it for scans. The Scan MCP is read-only.

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

No. The scan is made from the xSpeed servers, so the URL has to be reachable from the public internet. Private, local and password-protected sites are not scanned. Put the preview on a public address first, or use a different check for local work.

Ask it to read the scan history with get_speed_scan before it starts, then run a fresh scan after the change. Compare the graded run on the same device, because a scan that lost its Lighthouse run grades less of the rubric and is not comparable.

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 Codex

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 Codex.

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

Open xSpeed Hub Codex setup