AI-generated Key Takeaways
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          Managing sub-accounts requires an MCA, which cannot have product information itself, necessitating sub-accounts for merchants with products. 
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          Sub-accounts can be created either manually or automatically through the Content API. 
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          There is a default limit of 50 sub-accounts per MCA, but more can be requested. 
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          Manual sub-account creation involves signing into Merchant Center and using the accounts section. 
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          Automatic sub-account creation requires the merchant to accept the Google Merchant Center Terms of Service beforehand and uses the accounts.insertAPI method.
Summary
You can authenticate with an MCA to manage sub-accounts without setting up authentication for each sub-account. MCAs can’t have product information themselves, so you need to create sub-accounts for merchants that have their product information.
You can create sub-accounts manually or through the Content API for Shopping as described in the following sections.
By default, MCAs can manage a maximum of 50 sub-accounts. If you need more than 50 sub-accounts, you can request more with the quota form.
Manual steps
- Sign in to your Merchant Center account.
- Click Accounts.
- Click the + plus button.
- Accept the Google Merchant Center Terms of Service.
- Enter a name for the new account.
- (Optional) Enter a URL for the account.
- Click Save.
Automatic steps
- Choose the Terms of Service for the merchant's country and language. - The Terms of Service links don't work in an iframe. You may need to send the merchant a stored copy of the Terms of Service and have a way to keep your copy up to date. 
- Keep a record of the acceptance of the Terms of Service and be prepared to provide these records to Google if requested. 
- Use the - accounts.insertmethod of the- accountsservice to create a new sub-account.
See the Shopping samples for other uses of the accounts.insert method.