Can you build lightweight custom software plus your own MCP to hook it into Claude/ChatGPT for your own workflows?

Yes — an example given was someone who bought a firm with an old CRM she didn't like, so she used Claude Code to build her own custom CRM, then created an MCP on top of it to connect that CRM's data into Claude. Another example: rather than building a fully custom CRM, an existing application (Folk) was used and connected via MCP directly into Claude to customize a CRM to specific needs (tracking leads coming from email, LinkedIn, website, and podcast). This kind of build-your-own-tool-plus-MCP pattern is increasingly common for people who want a workflow tailored to their process.