I tried to add image with description via ios app. I can able to add description and posted , but after that in tweets it doesn’t show the description which i added .
This feels like a question about the iOS app, rather than the API and developer platform.
You can learn more about the launch of alt text for images on the consumer app blog. If you’re interested in the API, we will have documentation on dev.twitter.com soon, but this developer blog post explains how it works and how to retrieve the text.
If you need further assistance with our apps or website, feel free to use our Support pages - these forums are dedicated to developer discussions. Thanks!