Here are the classes, structs, unions and interfaces with brief descriptions:

[detail level 1234]

▼NSCIA
▼NOpenAPI
▼NModels
CErrorInfo	Error info
CErrorRepository	Error info repository
▼NResults
CMinMaxLayer	Class which provides information about Minimum and Maximum Layer index
CResult	Class treating the ResultsAPI instance based on the provided ResultKey
CResultKey	This class is used for definition of result you want to get
CResultsAPI	Class providing functionality for work with results storage in Scia Engineer. The initialization of RAPI can be done using the Structure.InitializeResultsAPI
CResultType	This class provides functions for work with ResultTypes. You can e.g. get supported magnitudes of the result type, get the result name, etc
▼NResultsCalculation
CCalculationRequest
CCalculationRunner
CResultPaletteItem
▼NStructureModelDefinition
CBeam	Provides methods for work with beams in the Scia Engineer model
CCombination	Provides definition of the combination in the Scia Engineer model
CCombinationItem	Provides content of the combination. Holds reference to the loadcase and it's coefficient
CCrossSectionManufactured	Provides methods for work with cross-sections created from prefabricated cross-section catalogues in the Scia Engineer model
CCrossSectionParametric	Provides methods for work with cross-sections created as geometrical shapes with parameters in the Scia Engineer model
CLineLoadBase	Base class for LineLoadOnBeam and LineLoadInSlabEdge. Holds common properties
CLineLoadOnBeam	Provides methods for work with line load on beam in the Scia Engineer model
CLineLoadOnSlabEdge	Provides methods for work with line load on slab edge in the Scia Engineer model
CLineSupport	Provides methods for work with line supports defined on beams and on slab edges in the Scia Engineer model
CLoadCase	Provides methods for work with load cases in the Scia Engineer model
CLoadGroup	Provides methods for work with load groups in the Scia Engineer model
CMaterial	Provides methods for work with materials in the Scia Engineer model
CPoint3D	Provides methods for work with 3D positions in the Scia Engineer model. You get new Point3D object e.g. when you call method for getting position of finite mesh element. Point3D is not used for definition of structural nodes - for structureal nodes we have the StructNode
CPointLoadFree	Provides methods for work point with free force in the Scia Engineer model. Free forces are used for generation of forces on 2D members
CPointLoadInNode	Provides methods for work with forces defined in structural nodes in the Scia Engineer model
CPointSupport	Provides methods for work with supports defined in structural nodes in the Scia Engineer model
CSlab	Provides methods for work with 2D members in the Scia Engineer model
CStructNode	Provides methods for work with structural nodes in the Scia Engineer model. Structural nodes are used for definition another structural entities like beams, slabs, etc
CStructureEntity	Parent class for the rest of model entities carying basic properties
CSupportBase	Base class for support in node and for line support. Covers common properties
CSurfaceLoad	Provides methods for work with structural nodes in the Scia Engineer model. Structural nodes are used for definition another structural entities
▼NUtils
COpenApiE2EResult	Scia result possible implementation
COpenApiE2EResults	Scia results possible implementation
CSciaFileGetter	Utility for getting basic Scia template file
CSciaOpenApiContext	Context for running OPEN API
CApiGuid	Class for treating unique identifiers for e.g. particular structural entities
CApiGuidArr	Class for treating unique identifiers array, e.g. for definnition of array of nodes for slab creation
CEnvironment	Treats the Scia Engineer environment - starts Scia Engineer, creates EsaProject, creates Structure, treats the communication between your application and Scia Engineer
CEsaProject	Treats the Structure and provides functionality regarding the Project like closing project, running analysis, etc
CStructure	Provides methods for work with the Scia Engineer model - definition of new entities, synchronization of model with Scia Engineer model, etc. Class is initialized in EsaProject.EsaProject(object, Guid)