07 Describe the process in order before asking for a drawing

What people usually ask

Draw a P&ID for a 50 litre biodiesel batch unit to ISA 5.1.

What comes back

A plausible flowsheet with guessed vessels, a continuous layout nobody asked for and instrument tags that fit no process.

Ask this instead

I am designing a 50 litre biodiesel batch unit. The steps in
order, from the first input:
1. <oil charged by hand into vessel 1>
2. <methanol and catalyst added, mixed, heated to 60 C>
3. <reaction held for 1 hour, then transferred to vessel 2>
4. <...>
These decisions are fixed: batch, two vessels, gravity
separation, no heat recovery. Replicate the layout of the
attached unit where my steps allow it.
Do not draw anything yet. Return a table of equipment and a
table of lines: tag, service, from, to, size if known, else
blank. I will check both tables before asking for the drawing.

Attach: the numbered step list and a datasheet or photo of the unit to replicate.

Why it works: the drawing can only be as right as the process behind it, so the process is stated first and the tables are checked before a line is drawn.