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. 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/CANkRMASt261kvOf2BR7LVnoqZ6vGh75jrTxUk%2Bvv3fWgEuff-Q%40mail.gmail.com.
