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Invoke a discovered WebMCP tool

Invokes the exact live registration identified by tool_ref. Non-autosubmit declarative form tools return after their fields are populated with an awaiting_submission status. Other tools wait for a terminal result, including across navigation. CDP-backed custom tool outputs above 240 KiB return an error rather than a truncated result. If the request times out after invocation begins, the server reports outcome_unknown and never retries the tool automatically.

post/webmcp/invoke

Request body

tool_refstring required
inputobject required

Tool input, limited to 1 MiB after JSON serialization.

timeout_secinteger

Response

Chromium accepted the invocation and either populated a non-autosubmit form or reported a terminal result.

invocation_idstring required
status'completed' | 'canceled' | 'error' | 'awaiting_submission' required

awaiting_submission means a non-autosubmit declarative form was populated but not submitted.

{"stackTrail":"components:schemas:WebMCPInvocationResult:properties:output","oasType":"schema","type":"unknown","description":"Untrusted page-provided output. Callers must treat it as potentially malicious input."}
error_textstring

Changes

Changed in 2 of the 65 revisions of this API.11