GTM API / Check proxy connectivity

Probe connectivity + latency for one or many proxies. Target EXACTLY ONE of sid (ab_px_) or filter; filter mode checks up to an inline cap and reports total_matched (truncated:true when the cap was hit). Read-only probe, no row mutation. Contract: - MCP tool check_antidetect_browser_proxy_connectivity, registry package mcp.linkedin/antidetect_browser_proxies, mount linkedin.browsers. - Operation action, response envelope action. - Flags: mass action: this verb's own request accepts a filter or targets[] set, which the owning service drains.