LGTM to experiment from M149 to M156 inclusive.
(Note: this looks like longer than usual, but we're switching to two
week releases in the middle - so it's still under the permitted 6 month
OT duration).
On 5/15/26 2:51 p.m., Chromestatus wrote:
*Contact emails*
[email protected], [email protected],
[email protected], [email protected], [email protected],
[email protected]
*Explainer*
https://github.com/webmachinelearning/webmcp
*Specification*
https://webmachinelearning.github.io/webmcp
*Design docs*
https://docs.google.com/document/d/1ZaQvuj4YnUnoqOfEhbfgFynpDRKk2zZZHavTNJ151gM/edit?tab=t.0#heading=h.ggi78l861caa
https://docs.google.com/document/d/1ycdzuXA-VE8lRDFSArh0Um3PChHV0Hq6Om1MSMG8qPE/edit?tab=t.0#heading=h.edohi3f5z12h
*Summary*
WebMCP is a proposal for a web API that enables web pages to provide
agent-specific paths in their UI. With WebMCP, agent-service
interaction takes place via app-controlled UI, providing a shared
context available to app, agent, and user.
*Blink component*
Blink>Agentic Platform>WebMCP
<https://issues.chromium.org/issues?q=customfield1222907:%22Blink%3EAgentic%20Platform%3EWebMCP%22>
*Web Feature ID*
navigator.modelContext (WebMCP)
<https://webstatus.dev/features/navigator.modelContext (WebMCP)>
*Search tags*
WebMCP </features#tags:WebMCP>
*TAG review*
Spec is being incubated. We will request TAG review before shipping.
*TAG review status*
Pending
*Goals for experimentation*
For the experiment we are focused on understanding the API ergonomics
for agentic workflows across various verticals such as web commerce
and productivity. We expect the site owners to implement WebMCP tools
in their sites to automate high-value workflows for them and will seek
feedback on the functionality of WebMCP. We also plan to gather
metrics for tool usage and latency, and assess opportunities for
improvements.
*Origin Trial documentation link*
https://docs.google.com/document/d/1ZaQvuj4YnUnoqOfEhbfgFynpDRKk2zZZHavTNJ151gM/edit?tab=t.0#heading=h.ggi78l861caa
*Risks*
*Interoperability and Compatibility*
Given this is a new space and new API - there's no compatibility risk.
Usual risk related to other browser vendors not adopting the API
apply. This API is meant to augment capabilities provided by browser
add-ons and so non-adoption in other engines would have limited
user-impact and thus we consider the risk to be low.
/Gecko/: No signal
/WebKit/: No signal
/Web developers/: No signals Web Framework developers: Have shown a
great deal of interest during the developer trial, as evidenced here:
https://www.star-history.com/?repos=webmachinelearning%2Fwebmcp&type=date&legend=bottom-right
<https://www.star-history.com/?repos=webmachinelearning%2Fwebmcp&type=date&legend=bottom-right>
Chrome web store features about 9 different extensions with WebMCP on
their title and 4* or more ratings.
https://chromewebstore.google.com/search/WebMCP?minimalRating=4
/Other signals/:
*Ergonomics*
There is a risk that site authors that wish to incorporate WebMCP
tools into their sites will need to duplicate functionality that
currently exists to drive the user interface. We're hoping that most
imperative WebMCP tools are just thin wrappers around existing code
that drives actions on the site, but we are working with framework
developers like React to ensure that WebMCP tools can be added without
rearchitecting the site logic. We are also offering a declarative
version that requires only adding attributes to existing form
elements, which is much lighter weight to deploy and does not require
any refactoring of existing site functionality.
*Activation*
There are no activation requirements to register WebMCP tools. To
execute WebMCP tools does require an agent, either provided by the
browser or site author, to formulate and orchestrate tool calls. There
are several Chrome extensions already available that allow
cloud-LLM-based agents to discover and call WebMCP tools. It is also
possible to use the Prompt API to call WebMCP tools using on-device
models.
*Security*
Sites may consume and expose sensitive information when their WebMCP
tools are called by agents. Agents should implement safeguards to
ensure that sensitive information is passed to sites and between
origins only under the consent of the user that is supervising them.
LLM-based agents are susceptible to attacks such as indirect prompt
injection, which can cause an exploited agent to exfiltrate sensitive
information in its context to an attacker. Agents should implement
safeguards against prompt injection and related attacks.
*WebView application risks*
Does this intent deprecate or change behavior of existing APIs, such
that it has potentially high risk for Android WebView-based applications?
/No information provided/
*Ongoing technical constraints*
No technical constraints for the experiments.
*Debuggability*
Explicit debugging support through a new WebMCP Chrome DevTools
Protocol domain. The domain supports listing registered tools,
invoking tools, and logging all calls by agents. Registration issues
for declarative tools (e.g., missing names or descriptions) are
reported through the Audits domain.
*Will this feature be supported on all six Blink platforms (Windows,
Mac, Linux, ChromeOS, Android, and Android WebView)?*
Yes
*Is this feature fully tested by web-platform-tests
<https://chromium.googlesource.com/chromium/src/+/main/docs/testing/web_platform_tests.md>?*
No
The IDL and basic usage is tested via WPTs. Since the API provides the
user agent with the ability to call certain tools, we might need to
extend the WPT harness to support this.
*DevTrial instructions*
https://docs.google.com/document/d/1rtU1fRPS0bMqd9abMG_hc6K9OAI6soUy3Kh00toAgyk/edit?tab=t.0
*Flag name on about://flags*
Experimental Web Platform features
*Finch feature name*
WebMCP
*Requires code in //chrome?*
True
*Tracking bug*
https://crbug.com/445637567
*Launch bug*
https://launch.corp.google.com/launch/4460611
*Estimated milestones*
Shipping on desktop 157
Origin trial desktop first 149
Origin trial desktop last 156
DevTrial on desktop 146
Shipping on Android 157
Origin trial Android first 149
Origin trial Android last 156
DevTrial on Android 146
Shipping on WebView 157
Origin trial WebView first 149
Origin trial WebView last 156
*Link to entry on the Chrome Platform Status*
https://chromestatus.com/feature/5117755740913664?gate=6226783774703616
*Links to previous Intent discussions*
Intent to Prototype:
https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CANMmsAtRdyRw1WtO5va0K%3D_adYH-FRh01xvw5%2BosSd_DAq%3D%3DUQ%40mail.gmail.com
Ready for Trial:
https://groups.google.com/a/chromium.org/g/blink-dev/c/bhhOmTGzD5Y/m/PGdM8lF6AQAJ
This intent message was generated by Chrome Platform Status
<https://chromestatus.com>.
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