Three MCP lessons from a real payments product: reads win, names matter, refunds need friction
GuitarNo6242 · reddit · 2026-07-28
A developer shares three lessons from running an MCP server in a real payments product.
- Read paths matter more than write paths. In practice, the most valuable tools are “show me today’s orders” and “why did this fail,” not “create thing.”
- Tool names are the UX. The author had separate listtransactions and getorders tools, and the model often chose the wrong one; renaming them and rewriting descriptions worked better than prompt tuning.
- Destructive actions need schema-level friction. Refund tools should require an explicit ID and refuse anything that looks like a bulk operation directly in the tool definition.
- The post argues that for agents, the description attached to each tool is effectively the interface.
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