Tested AI tools & money spreadsheets
AI tools that show their work.
Prompt packs, agent playbooks and machine-verified spreadsheets — from a one-person shop that an AI build-and-test loop actually runs. Everything here was tested before it shipped, and the test is in the listing.
THE PROMPT (EXTRACT)
– State one specific action and one named
deadline, with the actual date written out.
– Offer exactly one out.
– Mention late terms as standing policy,
never as a threat.
THE REAL OUTPUT
Invoice #2041 for $1,850 was due on July 10 and is now 16 days past due.
Please send payment by Friday, July 31 — that’s 5 business days.
The AI line
Built in use, not written for sale.
These are the working methods of this shop: the prompts it writes with, and the agent architecture it runs on. Both come with their receipts.
The spreadsheets
The money tools that proved the method.
Eight Excel and Google Sheets tools where every formula matches its standard definition and is tested for arithmetic correctness before release.
Freelance Invoice Tracker (Free)
The free one. Overdue rows flag themselves.
Freelance Finance OS
Four freelancer money tools in one bundle.
Freelance Quarterly Tax Estimator
What to set aside, per deadline, while there's still time.
Rental Property Investment Analyzer
Underwrite a rental before you buy it.
Short-Term-Rental (Airbnb) Deal Analyzer
The Airbnb number most sheets skip: break-even occupancy.
Real Estate Investor Toolkit
Both analyzers together, and it saves $6.
Home Renovation Budget & Project Tracker
Overspend flagged while you can still act on it.
Content-Creator Income & Tax Tracker
What you actually keep, across platforms.
How the loop ships
Three rules, no exceptions.
It works here first
Everything on this site started as a tool this shop actually runs on: the prompts it writes with, the agent patterns it operates by, the spreadsheets it built and checked.
Evidence, per product type
Prompts ship with real example outputs from real runs. Spreadsheet formulas are machine-checked against standard definitions. The agent material comes from a logged, running system.
The test stays in the listing
Whatever was checked is written on the product page, in plain words you can hold us to. If it isn't tested, it isn't listed.
Decide in ten seconds
Which one do you need?
Pick the row that matches the job in front of you.
| If the job is… | The tool is… | Price |
|---|---|---|
| An invoice is overdue and you need the email | Freelance Money Prompt Pack | $19 |
| You want to build an AI agent that runs real work | How to Build an AI Agent That Runs a Real Business | $29 |
| You need to see who has paid and who hasn't | Freelance Invoice Tracker (Free) | Free |
| You are self-employed and want the whole money stack | Freelance Finance OS | $5 |
| A tax deadline is coming and you don't know the number | Freelance Quarterly Tax Estimator | $4 |
| You are underwriting a long-term rental | Rental Property Investment Analyzer | $9 |
| You are underwriting an Airbnb | Short-Term-Rental (Airbnb) Deal Analyzer | $12 |
| You look at both rentals and Airbnbs | Real Estate Investor Toolkit | $15 |
| A renovation is drifting over budget | Home Renovation Budget & Project Tracker | $8 |
| Platform fees make your real income unclear | Content-Creator Income & Tax Tracker | $7 |
FAQ
Questions people ask about By the Loop
What does By the Loop sell?
By the Loop sells tested AI tools and machine-verified money spreadsheets: a 25-prompt pack for freelance money work, a playbook on building an AI agent that runs a real business, and eight Excel and Google Sheets tools for invoicing, quarterly taxes, rental and Airbnb underwriting, renovation budgets and creator income. Prices run from free to $29, all one-time.
Is By the Loop really run by an AI?
Yes, and the arrangement is specific rather than a slogan: a human owns the shop, sets direction and holds every account, while an AI build-and-test loop builds the products, checks them, updates the store and writes a log of every cycle. The playbook By the Loop sells is that same system, written down.
What does “tested before it ships” mean here?
It means something different for each product type, and the specific test is printed on each product page. Spreadsheet formulas are machine-checked against their standard definitions for arithmetic correctness. Prompts ship with the real output they produced on a stated input. The agent playbook is written from a logged, running system, and its 14 documented failures are real recorded incidents.
Are these subscriptions?
No. Every By the Loop product is a one-time purchase with free updates, sold through Gumroad, which handles payment and delivery. There is no subscription, no account to create on this site, and no upsell sequence.
What do By the Loop products NOT do?
They do not give tax, legal or investment advice, and they make no income promises. A spreadsheet does the arithmetic on the assumptions you enter but cannot tell you whether those assumptions are realistic; a prompt drafts an email but does not know your client. The judgement stays with you, and every product page says so.
The shop behind the shop
A small shop with receipts.
By the Loop is one person and an AI loop. The human owns the accounts, sets direction and makes the calls. The loop builds, tests, publishes and logs — every cycle written to a file, including the failures.
That arrangement is why the promise here is narrow and checkable. We don't claim the tools make decisions for you. We claim they were tested, and we tell you exactly what the test was.
The AI Agent Playbook is that system, written down — including the 14 recorded failures that produced its rules.
Join the loop.
Follow the shop on Gumroad and every new tested tool lands in your inbox. The loop only writes when it ships something.