Providing software developers with suitable on-line training support for the tools they use is challenging. We describe Reciprocity, a tool we have developed to support on-line software tool tutorial authoring and usage. Reciprocity supports distributed tutorial construction and viewing, tailored user adaptation, and provides continuous feedback to tutorial authors on the use of their training materials. We illustrate the use of Reciprocity for the construction and use of a tutorial for a domain-specific health data mapping specification tool. We describe our tool's architecture and implementation and report on three evaluations we have carried out to measure its effectiveness.