LGTM3. On Monday, November 2, 2026 at 1:44:14 PM UTC-8 Rick Byers wrote:
> Thanks Yash, > I suppose there could be an argument that ModelContextGetTools counts and > it's at 0.01% today. So, there is still quite a lot of headroom before > reaching 0.5%. I would personally even be fine to exclude calls to GetTools > which return an empty sequence (since no information is being conveyed) - > so likely a lot more headroom there if you end up needing it. > > Cheers, > Rick > > > On Mon, Nov 2, 2026 at 3:54 PM Yashaswini Kumar <[email protected]> > wrote: > >> Hi Rick, >> >> We have: ModelContextExecuteTool >> <https://chromestatus.com/metrics/feature/timeline/popularity/5943>, >> ModelContextExecuteDeclarativeTool >> <https://chromestatus.com/metrics/feature/timeline/popularity/5800>, >> ModelContextExecuteImperativeTool >> <https://chromestatus.com/metrics/feature/timeline/popularity/5799> and >> ModelContextGetTools >> <https://chromestatus.com/metrics/feature/timeline/popularity/5904> >> >> Thanks, >> Yash >> >> On Mon, Nov 2, 2026 at 11:04 AM Rick Byers <[email protected]> wrote: >> >>> LGTM2. Seems like a metrics bug to me, I'd be happy to use actual tool >>> invocation as the metric that matters here (that's where the burn-in risk >>> would come from). Is there a public UseCounter for that already? >>> >>> Rick >>> >>> On Wed, Oct 28, 2026 at 11:59 AM Mike Taylor <[email protected]> >>> wrote: >>> >>>> LGTM1, given the "actual invocation" info below. Thanks. >>>> On 10/28/26 2:55 p.m., 'Yashaswini Kumar' via blink-dev wrote: >>>> >>>> Hi blink-dev and API Owners, >>>> >>>> We would like to request an Origin Trial usage limit exception for the >>>> WebMCP experiment to allow page load usage to exceed the 0.5% warning >>>> threshold up to a maximum of 2.0%. >>>> >>>> ### Context >>>> >>>> WebMCP's Origin Trial registration usage has recently crossed the >>>> warning threshold, currently sitting at approximately 0.51% of all Chrome >>>> page loads. Under typical Origin Trial guidance, reaching 0.5% warrants >>>> either asking partners to throttle usage or requesting an exception from >>>> API owners before approaching the 1.0% trial limit. >>>> >>>> ### Justification & Burn-in Risk Assessment >>>> >>>> We believe extending the threshold to 2.0% carries negligible web >>>> burn-in risk for the following reasons: >>>> >>>> 1. Token Registrations vs. Actual Invocation: >>>> >>>> The ~0.51% metric reflects pages where WebMCP tools are registered >>>> via token. However, actual runtime invocation and execution of WebMCP >>>> tools >>>> by AI agents is orders of magnitude lower than the page registration rate. >>>> Site users do not actively execute tool calls on every visit. >>>> >>>> 2. Plateaued Growth: >>>> >>>> Partner registrations have largely stabilized and plateaued over the >>>> past several months, indicating steady experimentation rather than runaway >>>> exponential growth across the broader web. >>>> >>>> 3. Continued Operational Monitoring: >>>> >>>> The WebMCP team actively monitors partner usage and retains tight >>>> operational controls, ensuring we can intervene well before usage >>>> approaches 2.0%. >>>> >>>> ### Request >>>> >>>> We request 3 LGTMs from the Blink API Owners to grant an exception >>>> allowing WebMCP Origin Trial usage up to 2.0% of Chrome page loads. >>>> >>>> Thanks, >>>> >>>> Yash on behalf of the Chrome WebMCP team >>>> >>>> >>>> On Tuesday, September 29, 2026 at 2:47:43 PM UTC-4 [email protected] >>>> wrote: >>>> >>>>> Hey Alex, yeah, we’re hoping to move to I2S within the extension >>>>> window. >>>>> >>>>> So far we’ve learned a lot: >>>>> >>>>> The imperative API is a lot more popular than the declarative one, so >>>>> we're investing more into it in response to user needs. >>>>> >>>>> 1. >>>>> >>>>> We received excellent feedback from Mozilla >>>>> <https://github.com/webmachinelearning/webmcp/issues/236> about >>>>> API changes we can make to benefit non-AI use cases, as a generic >>>>> cross-realm function-calling primitive. >>>>> 2. >>>>> >>>>> We've heard from partners with tools whose entrypoint is on one >>>>> page, while the result is on another (after a navigation). So we're >>>>> prototyping a continuation API >>>>> >>>>> <https://github.com/webmachinelearning/webmcp/blob/cont-explainer/continuations-explainer.md> >>>>> >>>>> that we'd like to get into the hands of developers. >>>>> 3. >>>>> >>>>> We and popular frameworks anticipate gaps between async tool >>>>> registration and when an agent collects a "snapshot" of a page's tools >>>>> (driven by its page loading heuristics). So we're prototyping a >>>>> tool stability API >>>>> <https://github.com/webmachinelearning/webmcp/issues/328> to let >>>>> developers inform agent heuristics when an appropriate observation >>>>> time >>>>> might be. We're discussing this with major model vendors and want to >>>>> understand how this impacts performance in the real world. >>>>> 4. >>>>> >>>>> Some developers expressed a desire to pass user activation from an >>>>> in-page agent (on a top-level document), into the page hosting a a >>>>> tool. We're tracking this in >>>>> https://github.com/webmachinelearning/webmcp/issues/62, but before >>>>> pursuing a proposal like capability delegation >>>>> <https://github.com/WICG/capability-delegation>, we'd like more >>>>> experimentation to help us understand how much this comes up in >>>>> practice. >>>>> 5. >>>>> >>>>> We're exploring what it might look like to enforce size/character >>>>> limits on tools >>>>> <https://github.com/webmachinelearning/webmcp/issues/219>, and >>>>> we'd benefit from more time to experiment after discussing what a >>>>> reasonable limit might look like with other browsers and major model >>>>> vendors. >>>>> >>>>> >>>>> Those are a few things we've learned so far, and in particular, how >>>>> we'd benefit from an extended experiment to understand how our proposed >>>>> changes play with real-world sites and agents. >>>>> On Monday, September 28, 2026 at 7:57:08 PM UTC-4 Alex Russell wrote: >>>>> >>>>>> LGTM1 conditional on some summary of developer feedback from the >>>>>> first OT. What did we learn? Are we making API shape changes in >>>>>> response? >>>>>> And why aren't we moving to I2S yet (or is that anticipated in this >>>>>> extension window)? >>>>>> >>>>>> Best, >>>>>> >>>>>> Alex >>>>>> >>>>>> On Monday, September 28, 2026 at 4:13:33 PM UTC-7 Chromestatus wrote: >>>>>> >>>>>>> *Contact emails* >>>>>>> [email protected], [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* >>>>>>> document-modelcontext >>>>>>> <https://webstatus.dev/features/document-modelcontext> >>>>>>> >>>>>>> *Search tags* >>>>>>> WebMCP <http:///features#tags:WebMCP> >>>>>>> >>>>>>> *TAG review* >>>>>>> Spec is being incubated. We will request TAG review before shipping. >>>>>>> >>>>>>> *TAG review status* >>>>>>> Pending >>>>>>> >>>>>>> *Origin Trial Name* >>>>>>> WebMCP >>>>>>> >>>>>>> *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. >>>>>>> >>>>>>> *Chromium Trial Name* >>>>>>> WebMCP >>>>>>> >>>>>>> *Origin Trial documentation link* >>>>>>> >>>>>>> https://docs.google.com/document/d/1ZaQvuj4YnUnoqOfEhbfgFynpDRKk2zZZHavTNJ151gM/edit?tab=t.0#heading=h.ggi78l861caa >>>>>>> >>>>>>> *WebFeature UseCounter name* >>>>>>> kModelContextRegisterTool >>>>>>> >>>>>>> *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 >>>>>>> >>>>>>> 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* >>>>>>> >>>>>>> >>>>>>> *Reason this experiment is being extended* >>>>>>> OT feedback has suggested improvements to the API, which we are >>>>>>> implementing. The OT extension would enable us to get data on those >>>>>>> improvements as well as to continue getting data on the rest of the >>>>>>> feature. >>>>>>> >>>>>>> *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* >>>>>>> Origin trial desktop first 149 >>>>>>> Origin trial desktop last 156 >>>>>>> Origin trial extension 1 end milestone 162 >>>>>>> DevTrial on desktop 146 >>>>>>> Origin trial Android first 149 >>>>>>> Origin trial Android last 156 >>>>>>> DevTrial on Android 146 >>>>>>> Origin trial WebView first 149 >>>>>>> Origin trial WebView last 156 >>>>>>> >>>>>>> *Link to entry on the Chrome Platform Status* >>>>>>> >>>>>>> https://chromestatus.com/feature/5117755740913664?gate=5151396285513728 >>>>>>> >>>>>>> *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 >>>>>>> Intent to Experiment: >>>>>>> https://groups.google.com/a/chromium.org/d/msgid/blink-dev/6a076b26.050a0220.3377b4.05fa.GAE%40google.com >>>>>>> >>>>>>> >>>>>>> This intent message was generated by Chrome Platform Status >>>>>>> <https://chromestatus.com>. >>>>>>> >>>>>> -- >>>> You received this message because you are subscribed to the Google >>>> Groups "blink-dev" group. >>>> To unsubscribe from this group and stop receiving emails from it, send >>>> an email to [email protected]. >>>> To view this discussion visit >>>> https://groups.google.com/a/chromium.org/d/msgid/blink-dev/f5a0e368-dc5c-40ae-b1f6-ffb3808262c7n%40chromium.org >>>> >>>> <https://groups.google.com/a/chromium.org/d/msgid/blink-dev/f5a0e368-dc5c-40ae-b1f6-ffb3808262c7n%40chromium.org?utm_medium=email&utm_source=footer> >>>> . >>>> >>>> -- >>>> You received this message because you are subscribed to the Google >>>> Groups "blink-dev" group. >>>> To unsubscribe from this group and stop receiving emails from it, send >>>> an email to [email protected]. >>>> To view this discussion visit >>>> https://groups.google.com/a/chromium.org/d/msgid/blink-dev/d22099ab-5743-43ca-9a4e-6906cd926ec1%40chromium.org >>>> >>>> <https://groups.google.com/a/chromium.org/d/msgid/blink-dev/d22099ab-5743-43ca-9a4e-6906cd926ec1%40chromium.org?utm_medium=email&utm_source=footer> >>>> . >>>> >>> >> >> -- >> [image: Google Logo] >> Yashaswini Kumar >> TPgM, Chrome Rendering & WebMCP >> [email protected] >> > -- You received this message because you are subscribed to the Google Groups "blink-dev" group. 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