WebMCP Readiness

WebMCP lets a page hand AI agents a list of callable actions instead of making them guess their way through your buttons from a screenshot. This decides whether you should build any, shapes them if you should, and stops you publishing claims the evidence does not support.

This file is the Claude Code wrapper. The same content is at AGENTS.md in the repository root for every other agent runtime.

Most sites should not build WebMCP tools yet. Returning that answer with the reasons is a successful run.

Routes

The flow is assess then design then implement then scaffold then verify then trial. review and claims are usable at any point.

Working templates are in templates/. Every one is checked by scripts/check-templates.sh for the deprecated accessor, the annotation contract, signal threading and name budgets.

Method

1. State the maturity position first, not as a closing caveat. Read claims-and-maturity. A reader acts on the recommendation and skims the disclaimer, so the disclaimer cannot carry the load.
2. Separate the four questions people conflate: can agents reach this site, can they read it, can they act on it, does any of it affect ranking. WebMCP answers only the third.
3. Run the fit assessment. Four tests, in method. Three or four passes is a scoped build. Two is defer with a date. Fewer is no.
4. If building, design against api-reference. Enforce the annotation contract and check both silent-failure gates.
5. If adjudicating a claim, apply the claim ladder. Return the exact supported wording, and name each failing claim with the reason.
6. Write the measurement plan and its limits. No external telemetry exists.

What this will and will not do

It WILL write tool code into your repository, scaffold it into your framework, and tell you how to verify it.

It will NOT:

• Claim WebMCP affects rankings, indexing, crawling, traffic, or conversion. No current evidence supports any of them.
• Deploy. It does not enrol you in an origin trial, set browser flags, install extensions, run a CLI against production, or modify a live site. Those are the owner's actions.
• Present a vendor benchmark as independent validation.
• Invent a statistic, a deployment, a capability, or a currentness claim. Missing evidence returns no data. Missing decisions return needs_input.
• Build before assess passes. Most sites should not have tools yet, and returning that answer with reasons is a successful run.

The one fact that governs every marketing claim

Chrome's own documentation:

"Clients and browsers must visit a site directly to know if it has callable tools."

There is no registry, no directory, no crawl path. An agent must already be on your page. WebMCP cannot bring you traffic. It changes what happens to traffic you already have. Third-party directories exist; no agent client is documented as reading them.

Volatility

Every fact here was verified against primary sources on 2026-09-05 and re-verified 2026-09-06 by a three-lane audit that corrected six errors. WebMCP is pre-standard and moves weekly. consequentialHint was two days old at capture. The Chrome origin trial ends 2026-11-17.

Re-verify before 2026-12-01, or immediately if any browser ships WebMCP by default. Treat an expired horizon as a blocker, not a warning. Sources and dates are in docs/sources.md.

Evaluation

Synthetic cases in evals: a good fit, a poor fit pushed enthusiastically, a claim adjudication, a security review, and a missing-evidence refusal. Case definitions are not a passing run. Nothing here has been through an independent behavioural evaluation.