Improve Input Validation

[aliviahossain]

A robust API should handle bad input gracefully. Currently, if you provide a non-numeric value for the size parameter, the API crashes with a "500 Internal Server Error". A better approach is to validate the input and return a user-friendly "400 Bad Request" error.

PLEASE ASSIGN ME THIS ISSUE UNDER THE GSSOC' 25 LABEL. THANK YOU.

[github-actions]

Thank you for raising this issue!

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Meanwhile make sure you've visited the README.md, CONTRIBUTING.md, and CODE_OF_CONDUCT.md before creating a PR for this. Also, please do NOT create a PR until this issue has been assigned to you. 😊

[Gupta-02]

Assign me this