Using entity in calls to functions that expect queries?

I'm just getting started with FeatureScript, so this is probably really naive... but I've scoured the docs and done a lot of trial/error, and I'm still mystified.

I'm trying to create a feature to that makes ribs from edges that are the intersections of two faces, with the rib following a vector that's halfway between the two faces. 

Here's the code in question:

                var averageNormal = vector(0, 0 , 0);
                const adjacentFaces is Query = qEdgeAdjacent(edgeProfile, EntityType.FACE);
                if (evaluateQuery(context, adjacentFaces) == []) {
                    throw regenError("Edge has no adjacent faces", edgeProfile);
                }
                for (var face in adjacentFaces) {
                    const faceNormal = evFaceNormalAtEdge(context, {"edge" : edgeProfile, "face" : face, "parameter" : 0.5});
                    averageNormal += faceNormal;
                }
                normalize(averageNormal);

The problem, I think, is that

var face in adjacentFaces

gets me an entity of EntityType.FACE. And evFaceNormalAtEdge wants the face to be a Query, like all of the ev* functions.

What am I missing? I realize there are complexities here with curved faces and the direction of the x-axis on the two faces. But I'm not even getting far enough to have those problems; I'm less worried about the accuracy of the algorithm than the language mechanism of "I have an entity and need a query".