In the docs for the language section of the module https://graphql.org/graphql-js/language/ There are two undocumented types needed by callers: `Document` returned by `parse()` https://graphql.org/graphql-js/language/#parse the AST node (mentioned as _value_) returned by functions in the `visitor` argument to `visit()` https://graphql.org/graphql-js/language/#visit Also these functions' argument types aren't fully documented: `print()` - https://graphql.org/graphql-js/language/#print `visit()` - https://graphql.org/graphql-js/language/#visit I'm using this module to obtain and manipulate a query AST, so docs for AST types would greatly help :) Btw, I'm calling this module in a browser context, for a new GraphQL client.