What it is
How many kilobytes of HTML you send, and how long the first response takes.
This is about the document itself, not your Lighthouse score — inline scripts and serialised state count, images mostly don't.
Why an agent cares
An agent working within a context window truncates. What survives is the top of the document; what gets dropped is the bottom — which is usually where your proof, pricing and contact details live.
Slow responses also get abandoned by clients with short timeouts, and you never see the failure.
How to fix it
- Trim inline scripts and large serialised state blobs from the initial document.
- Target under 500 KB of HTML on key pages.
- Put the substance early in the document, not after 300 KB of nav and hero markup.
How we test it
We measure the bytes of the homepage response and the time to complete it.