Chatbot - Keep it simple & short
Most of us in our lifetime would have definitely installed a software, right? How many of us remember the terms and conditions for that software, anyone? I am pretty sure none of us. As we don’t find it useful, we think who is going to read the whole bunch of text, we just click ‘I agree'. Same goes with chatbots.
When users lands in our bot they first encounter a welcome message followed by some actions or probably a question. This initial text/question is one of the most important information for the users. And if this message is too long, then the users are less likely to spend time reading it. This holds true for any conversations that follow. Long instructions make the users skip them and miss some necessary info that you would have wanted your users to know.
Also considering the chat interface, having long convo requires the users to scroll back and forth to read it completely resulting in the texts being overlooked and users are less likely to follow the long messages.
So, always try to keep your texts or conversations short. Yes, it might happen sometimes you need to put a larger content, in such cases you can divide the content into smaller fragments and provide an action button which will forward the users to the next message. Design your messages in such a manner, that the users are engaged and is likely to tap the action button.
Also I believe that the initial message should be kept within 200 characters, anything beyond that falls in tl;dr. If the instructions are too large, then put a help button among initial actions. This button can explain the users about any other required information you want them to know.
Before sending the bot to live audience, give the bot to your friends or colleagues. Let them use it and ask them did they read the instructions or messages provided, did they understand and follow? or they simply skipped those messages. Collect their feedback and keep on modifying your bot convo until you and your friends find the messages short, simple and useful.