Host toolchain resource

automobile:host/toolchain is a read-only diagnostic MCP resource. It reports host-tool availability for adb, emulator, sdkmanager, avdmanager, xcodebuild, xcode-select, xcrun, simctl, and devicectl.

Its JSON content has a lastUpdated ISO-8601 timestamp and an entries array. Each entry has a canonical name and available boolean. version and location are included when known; an unavailable entry includes error when there is a specific probe failure.

location is reported only when the probe returned an absolute path (POSIX or Windows drive-letter); a bare command name such as adb is omitted.

Every probe races the doctor check against DOCTOR_EXEC_TIMEOUT_MS. When the deadline wins, the entry reports the timeout and the resource aborts the losing check through the DoctorProbeOptions signal, so the commands it spawned (for example emulator -list-avds or an adb path probe) are killed rather than accumulating across repeated reads (#7008).

version and location are advisory information and must not gate automation. available for adb, and for at least one Apple developer-tooling entry, is an operational requirement for the corresponding AutoMobile device automation. This resource itself is diagnostic only: it does not gate any tool call, change host state, or enumerate devices. Doctor and readiness gating remain separate and are unaffected.