No worries, think your interpretation of just api calls is a good one, a bit like "tests as documentation". Could then have another tour for each module (api implementation). This approach would tend to confine the effect of changes (as in Parnas' On the Criteria To Be Used in Decomposing Systems into Modules https://www.win.tue.nl/~wstomv/edu/2ip30/references/criteria...)

Though multiplicity of tours is also complexity!