Read-only MCP was easy. Here's what changed once our agents could write back
A team ran MCP-based agents read-only for months with no unrecoverable failure, then had to rewrite every rule the day agents got write access. The lesson: read-only failures are free, write failures are permanent. Suggested safeguards include per-tool budgets, confirmation for irreversible actions, and tiered trust where new tools earn write access gradually.