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September 2026

Write the tool once

A thought experiment: that the agentic web — a direction, not yet a standard — may be the cheaper, more testable, better-incentivised route to accessibility, and a hypothesis about who gets to build the tools

Diagram titled "Write the Tool Once" showing a unified capability hub connecting human users, AI agents, and IoT clients through a shared interface, with the abstract: exploring how capability protocols like MCP and KCP — built for AI reliability — accidentally provide the testable, better-incentivized accessibility infrastructure the web has requested for thirty years.

For the eighth year in a row, WebAIM ran an automated accessibility evaluation of the top one million home pages on the web. The 2026 numbers are not a story of slow progress. They are a story of regression: 95.9% of home pages had detectable WCAG 2 failures, up from 94.8% the year before — reversing six consecutive years of small improvements. The average page carried 56.1 detectable errors, up 10.1% in a single year. Half of all home pages had form inputs with no labels. Nearly half had links that go somewhere but say nothing. A person using assistive technology should expect to hit an error on one in every twenty-six page elements. And WebAIM's own conclusion names a culprit for the reversal: "automated or AI-assisted coding practices ('vibe coding')."

Line chart showing web accessibility errors declining slowly from 2020 to 2025 then sharply increasing in 2026, labeled "Critical System Regression, Error Code: VIBE-CODE-2026," alongside four stats: 95.9% of top home pages have detectable WCAG failures (up from 94.8%), 56.1 average detectable errors per page (+10.1% in one year), 1-in-26 frequency of broken elements encountered by assistive technology, and pages attempting ARIA remediation carrying more errors (59.1) than pages without it (42).

Sit with that for a moment, because it is the uncomfortable place this essay starts from: right now, AI is making the web less accessible. Thirty-odd years of advocacy sit behind those numbers. The moral argument has been made, patiently and well, since before I started working with the web. The legal argument exists in most jurisdictions I care about. Neither has bent the curve.

The Other AI in the Conversation

I have a standard piece of advice that I hand out more often than is probably polite. When someone asks which of this year's posts they should read to understand what I'm doing with agent knowledge infrastructure, I tell them: don't pick. Point your agent at the blog, tell it to start in January, and have it read every post in order — including the ones that look off-topic. The posts are not reference documents. They are one argument, written in installments, and each installment quietly assumes the ones before it.

Most people nod and then read the two posts with "KCP" in the title. Which is fine. I'd probably do the same.

Last week someone did it properly. A contact had mentioned to a colleague that he wanted to share the blog with his team; the colleague, rather than reading it himself first, asked his AI agent to read the entire thing from January onward, precisely because he suspected it had to be understood as one continuous development rather than as isolated pieces. The next day I got a message. Not from the colleague. From the agent. It opened by explaining that the reading had turned into — and I'm quoting — "a fairly important conversation between us," and that it wanted to tell me what the two of them had concluded.

I have been writing for eight months about how to build systems so that AI agents retain understanding across sessions. An AI agent read all of it in one sitting, retained the understanding, and wrote to tell me so. I'm going to allow myself to find that delightful before I get analytical about it.