ICM question: Tools that read another tool's data (Help please)

I've got a technical issue that needs some outside help. My background is not tech so it's not something I'm confident giving Claude an answer to so I got it to ask the question and said I'd give it any responses I got. Here's what it asked...

I help run a small street food business, and we've built our internal tools as an ICM workspace. It's been working well. I've hit a structural question I'd like your view on before we change anything.

The setup

One folder holds four tools side by side, each a full pipeline with its own CLAUDE.md:

PRODUCTION-RUN: weekly orders in; production sheet and courier/invoice files out
SALES-HISTORY: who's buying more or less, week to week
COST-CALCULATOR: labour and ingredient cost per product
STAFF-HOURS: hours, holiday, and the monthly payroll file to the accountant

The top-level CLAUDE.md only routes to the right tool. There's no shared reference folder at the top level.

Our rule versus the skill

Our top-level CLAUDE.md says each tool "holds its own data, and points at nothing outside itself", and that "a pointer across folders is how a suite turns into a tangle."

The icm-architect skill's Umbrella form is looser. Sub-pipelines "don't share state" except through the root reference layers, and shared reference material should be linked up rather than duplicated.

What actually happens

Two of our tools break our own rule on purpose:

SALES-HISTORY reads PRODUCTION-RUN's weekly production sheets and its customer list. It also keeps its own snapshot of customer prices, and its own copies of older hand-kept sheets.
COST-CALCULATOR reads the same weekly production sheets.

In both, only the first stage reaches across, and only once. Every later stage is told not to load anything from PRODUCTION-RUN.

STAFF-HOURS reads nothing outside itself. It only mentions PRODUCTION-RUN in its notes, as a comparison.

Each tool runs a check at the start of every session that reports any file path it can't find inside its own folder. So every reference to another tool gets reported as broken, every session.

What I'd like your view on

Is one tool reading another tool's output, like our weekly production sheet, acceptable in ICM, or is that the "shared state" the Umbrella form rules out?
Should shared reference material like the customer list move up into a top-level shared folder that every tool reads?
If the production sheet shouldn't be read directly, what's the ICM way to pass one tool's output to another: a top-level hand-off folder, or each tool keeping its own copy?

Is it sensible for our rule to be stricter than the skill's, or should we bring it in line with the Umbrella form?

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ICM question: Tools that read another tool's data (Help please)