Why this build, here
Suppliers in Zambia quote in kwacha from price lists often set in dollars, then add VAT. Models are bad at arithmetic and good at deciding what to do next. Tool calling gives each job to the right side.
The build, step by step
Write the tools as plain functions
Describe them well
Write the loop yourself
Handle tool failure
Trace a run
The steps, checks and practice open with a code
You can see what this lesson builds. The detail of each step, the finished-when checks and interview scoring come with the K850 practice, along with weekly build sessions and code review.
Read and run
Interview practice
Questions on this topic from AI Engineering Interview Questions, company-wise, with the companies it lists. Write your answer the way you would say it; Jev scores it and DeepSeek tells you what to add.
Scoring opens with an access code. You can still read the questions and prepare.