Is there an available tool (low-cost pay, or free) which would allow the specification of an originating city, an airline, and a fare basis and would then display all possible destination city-fare pairs covered by that triplet?

A fare basis applies to both an origin and destination pair, not just an origin point.

Are you looking for something to interpret the routing rules or a list of all fares from one place on a particular carrier?

Ya - grokked that the basis applies to A and to B. I'm looking for the latter, sort of (a list of all fares from an origin, on a particular carrier (potentially given a fare basis) - and dates, of course).

So for example, i would say CDG, LX, JICSWIFR, 14.nov-20.nov and receive a list featuring NRT - $XXX, BKK - $YYY, etc etc.

(Though i'd still be interested were i just to specify CDG, LX, 14.nov-20.nov).

This is possible using ITA, multiple destinations and the 300 mile radius. Have you tried that yet?

The problem with the first example you gave is that the fare basis (JICSWIFR) will not necessarily exist in more than one market so it doesn't make sense to search on it.

I haven't tried that yet; i'll investigate the ITA help more thoroughly - danke.

Hmmm, i feel like we're miscommunicating here... using the example i gave - the fare basis does exist in more than one market (if i understand our usage of the word 'market' as destination), but even were it to exist in only one market (or none in the case of an invalid fare basis specified), there's nothing wrong with a search result returning an empty set and a single result.

In other words, aside from it being potentially impossible with the query language, "give me all valid destinations with their accompanying fares for originating city A, on airline B, with fare basis C, for dates D and E" seems like a totally valid question to pose of the data set... no? (I guess that's rhetorical as you seem to be saying 'no'. It just seems that this query is abstractly no different than 'give me all valid fare basis with their accompanying fares for originating city A, on airline B, for dates D and E, and destination F'.)