Ingalls Shipbuilding successfully completed acceptance trials for the Coast Guard’s ninth national security cutter (NSC), Stone, in October 2020. NSC Stone was accepted Nov. 9, 2020, by the Coast Guard in a socially distanced ceremony. Photo by Lance Davis of Huntington Ingalls Industries.
During the Cold War, every US Navy task force was nearly always accompanied by a little friend, a Soviet AGI.
Oct 28, 1969 – The Soviet intelligence trawler Gidrofon underway with the attack aircraft carrier USS Coral Sea (CV-43) and her escort ships in the background.
The Soviet Intelligence Ships would provide near constant updates of the position of US carriers and the ships that were with them.
The recent transit of a group of Russian ships, shadowed by US, Canadian, and French ships and aircraft, including USCGC Stone, got me to thinking how the National Security Cutters (NSC) are an almost perfect asset to tail potentially hostile surface vessels during periods of heightened tension.
They are well equipped to keep surface threats under surveillance and provide continuous updates of their position and activities to cooperating units and the National Command Authority. They have a data link and a Sensitive Compartmented Information Facility (SCIF).
NSCs have other advantages over the typical Soviet AGI of the cold war period. They are much faster (28 knots) and are normally equipped with both manned and unmanned aircraft that could maintain surveillance for a long time even if a faster ship tried to outrun it.
Though certainly not a match for a ship like the Admiral Gorshkov, If an NSC observed a hostile act like a missile launch, it could potentially respond and might be able to inflict some damage. If a DDG were in the same position it might also be overwhelmed by a surprise attack. Having an NSC do the shadowing would allow other assets like the DDGs to remain over the horizon, complicating targeting for the adversary and insuring at least some time to respond if the situation goes hot.
Chuck Hill's CG Blog 
I am wondering if the NSC has the capability for a wartime role as AGI, along with Escort and Anti Surface warfare.
You mean a real frigate for a real frigate tasking? I think OPC could do this too. They might outrun it for awhile but it would generally keep pace. Especially if the navy tweaked it a bit for its own flight of light frigates.
I think NSC are too large and needed for other missions. While more recent AGI ships have been larger than C-2 size, and some OSV types. I would look at the T-AGOS type and size of ship for an AGI role. There maybe some in reserve fleet?
One T-AGOS used radar and blimps to do surveillance for the Joint Interagency Task Force JIATF-S in Key West. Nearest ship we have have like an AGI in the last 30 years.
I will send you a couple of pix
I was thinking of this as a part time job, when potentially hostile surface ships show up near the US, just as a National Security Cutter shadowed a Russian/Chinese task force transiting near the Aleutians not too long ago.
The new T-AGOS are for towing very large sonar arrays at slow speed. Not what I had in mind.