Shopify to Vinted/Grailed Crosslist Integration

I'm looking for a skilled freelance developer with experience in e-commerce integrations to build a custom application (either web-based or embedded in Shopify) that allows me to crosslist products from my Shopify store (Spain-based) to Vinted FR and Grailed.

I currently sell exclusively on Shopify, Vinted and Grailed but I need to streamline the workflow to:

Upload ~2,000 historical products from Shopify to Vinted FR and Grailed.

Keep listings and stock synchronized across platforms.

Use the tool weekly for 500+ products per month.

Core Features Needed:

Import from Shopify (Drafts or Published):

Filter or manually select products by tag or date.

Preview and edit listing before crossposting.

Crosslisting to Vinted FR and Grailed:

Category mapping system between platforms.

Finalize titles and descriptions with placeholders or templates.

Upload images and product variants.

Publish directly or export-ready for quick manual upload.


Stock Synchronization:

Manual stock checks between platforms.

Notify or pause listings if sold on one marketplace.


Weekly Maintenance:

Upload products listed on Shopify 30 days ago.

Regular updates and technical adjustments.


Requirements:

Proven experience with Shopify API and ideally Vinted and Grailed (or workarounds for platforms with limited API access).

Familiarity with crosslisting tools like Vendoo or SellerAider is a strong plus.

Must deliver a tool that is easy to use, reliable, and built for recurring weekly use.

Open to a monthly maintenance agreement.


What I’m Looking For:

A clear proposal on whether the project can be fully automated — and how.

Manual fallback plan if API limitations prevent full automation.

Description of your relevant experience and preferred tech/tools.

Estimated timeline and support model after launch.