API creates rows but strips out all cell values

I am attempting to write data into Smartsheet using the API, but every POST request that adds a row results in all cell values being removed. The API call returns SUCCESS, a new row is created, and the row number increments correctly, but every cell in the row is blank. This happens consistently with all sheets, even with brand-new sheets I created myself that contain only simple Text/Number and Date columns. I have full System Admin access, and there are no formulas, column locks, automations, or data restrictions on these sheets. I tested with multiple API tokens, including newly generated tokens, and the behavior is the same. I also tested using the official Smartsheet API “Try It Now” console, and it produces the same result—rows are added but cell values are silently stripped. This indicates the issue is not with my code but likely an account-level API write restriction or backend configuration. I need assistance identifying and removing whatever is preventing API write operations from saving cell values.

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jjg279

Aloha! I apologize if this seems like a silly question, but are you actually building data into your row before you POST it? I was adding rows to a sheet this week (using python) and the code looked like this:

I had to create a row, then populate it, then add it. If you aren't populating it that might be the issue?

donken

Thank you for the response. I am sending cell values. The issue isn’t that the row is empty—Smartsheet is silently discarding the values even though the POST is SUCCESS. This usually happens when columns contain formulas, links, or read-only rules, which I have ruled out all of those scenarios. Here is a snippet of the C# program we are using. We are 100% sure the problem is not with our code. There appears to be some sort of write restriction on the api key perhaps?

cmhorn

Get your sheet's column structure:

   GET https://api.smartsheet.com/2.0/sheets/{sheetId}

Compare the returned column IDs with what you're using in your POST.

Check column types in the response - make sure your values match:
- TEXT_NUMBER: "value": "string"
- DATE: "value": "2025-11-19"
- CHECKBOX: "value": true
- CONTACT_LIST: "objectValue": {"objectType": "CONTACT", "email": "user@example .com"}
Check the full API response body for any warnings or additional error details beyond just SUCCESS status. Might shed some light? For me, tricky issues often hide behind looking at the activity from the API's perspective.

Paul Newcome

Have you checked the activity log and cell history to see if the data is being populated but then cleared as opposed to not passed at all?

donken

I wanted to follow up and let everyone know that I resolved the null-value issue I was seeing when adding rows through the API. The problem was that the column IDs in my code did not match the actual column IDs from the sheet, so the API was accepting the request but placing the values into non-existent columns, which resulted in nulls being returned. Once I pulled the correct column IDs using a GET request and updated the code, everything worked perfectly so sharing this in case it helps others troubleshoot similar behavior.

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