Reviewing and revising contracts
Upload a Word contract, have it checked against your checklist and get the corrections back as tracked changes in the original document.
A contract needs updating to new fees, checking against an internal checklist or comparing with an earlier version. Custodos reads the contract, gives you a review you can check and, on request, writes the corrections into your Word file as tracked changes. Letterhead, formatting and tables are kept.
The example: Lea Keller of Kieselmatt Treuhand AG updates the client contract with Holzwerk Brunner GmbH to the Fee Schedule 2026 and checks it against the New Client Checklist.
Preparation
- Word rather than PDF. Custodos can change text in a Word file (.docx). In a PDF it can only remove, reorder, rotate or merge pages, not change the wording.
- Have the references ready. At Kieselmatt, the Fee Schedule 2026 and the New Client Checklist are in the brain "Firm handbook". Alternatively, attach them as a second and third file.
- Choose security mode. The contract contains client data. Turn on security mode in a new chat with the lock in the message box before you send the first message. If your workspace does not offer it, work with pseudonymisation.
Workflow
Attach the contract
In the message box, click Add and then Attach file, or drag the file into the chat. Under Brain, select the brain with the fee schedule and checklist.
If Custodos detects names, addresses or account numbers in the contract, a notice below the message box shows how many. Company names such as "Holzwerk Brunner GmbH" are usually not detected. Open the list from the notice and add the name with Add; it then goes to the model as a placeholder for the whole chat.
Review first, change nothing yet
Keep the review and the changes apart. That way you see every suggestion before it lands in the document:
Attached is the client contract with Holzwerk Brunner GmbH. Check it against the New Client Checklist and the Fee Schedule 2026 from the brain. Do not change the file yet.
Pay particular attention to: scope of the engagement, hourly rates and flat fees, payment terms, notice period, limitation of liability, retention of records and data protection.
Reply with a table: no., item, location in the contract (clause and verbatim quote), finding, suggested new wording. Say so if the checklist or the fee schedule has nothing on an item.
Check the review
A table comes back, for example: clause 4.1 still states the 2025 hourly rate, clause 9 has no rule on retention of records, the notice period in clause 11 differs from the checklist.
Check every row:
- Is the quote really in the contract as written? Search for it in Word.
- Do amounts and deadlines match the fee schedule and checklist? The brain sources appear below the answer and can be opened.
- Is an item missing that you expected? Ask: "Did you check the rule on VAT?"
Delete or correct suggestions in the chat before you move on.
Have the changes applied as tracked changes
Say exactly which suggestions go into the document, and ask for tracked changes:
Apply suggestions 1, 2 and 4 as tracked changes directly in the contract. Leave out suggestion 3. Make no other changes.
While it works, the answer shows Editing Word file…. Afterwards a new file appears below the answer for download, for example "Client-contract-Holzwerk-Brunner-bearbeitet.docx". Your original file stays unchanged.
Accept or reject in Word
Open the file in Word. Every change appears as a revision by the author "Custodos", or the name your workspace shows instead of Custodos. Go through the changes one by one and accept or reject each. Watch out for cross-references and terms defined elsewhere in the contract.
What makes this workflow safe
| Feature | What it does here |
|---|---|
| Pseudonymisation | Names, addresses and account numbers go to the model as placeholders. The edited file contains the real values again. |
| Security mode | Only the model your admin chose for it, always pseudonymised, no web search, no Send original. |
| Tracked changes | Every change is visible and only becomes part of the contract with your approval. |
| New file | The original stays as it was. The result usually carries the suffix "bearbeitet" in its name. |
| Technical check | Before the file appears, Custodos checks that it opens. You check the content. |
Variations
- Compare two versions. Attach both versions and ask: "List all substantive differences between version A and version B as a table with clause, old and new." The model compares texts, it is not an exact comparison tool. For a complete comparison, also use Word's compare feature.
- Review a supplier contract from your side. "Mark clauses that are unusual or disadvantageous for us as the customer, and give a short reason."
- Update an employment contract. For Bäckerei Mehlwerk GmbH, for example, enter new working hours, in security mode because pay and personal details are in it.
Limits
Best practices
- Review first, change afterwards, each in its own message.
- Ask for verbatim quotes as locations. You check faster, and the change lands in the right place.
- Work with one contract per chat.
- Keep the checklist and fee schedule in a brain instead of attaching them every time.
- If the same review is needed regularly, turn it into an agent. See Building good agents.
Frequently asked questions
Write "as tracked changes" explicitly in your message. Without that request, changes are written straight into the text.
No. In a PDF, only pages can be edited. Custodos can write the content as a new Word or PDF document, but the original layout is lost. Ask for the Word version if possible.
Usually the file is larger than 4 MB, in the old .doc format, or imported from Google Drive or Microsoft 365 instead of uploaded directly. Upload a .docx file directly. Also check that the chosen model can create files.
Custodos, or the name your workspace shows instead of Custodos. The model itself never appears as the author.
Next steps
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