MCP File Handling: Why Your Base64 Upload Breaks at 4MB

Logosofia no Dia a Dia · Apr 27, 2026 · 24m

The Model Context Protocol has a dirty secret: there's no standard way to pass files between servers and clients. Base64 encoding hits hard 4MB limits, burns through token budgets, and fails silently in production. Presigned URL patterns require manual domain whitelisting that non-technical users can't manage. And while some builders run MinIO S3 buckets on their MCP servers, every implementation reinvents the wheel differently. This episode unpacks SEP 2356 — the draft proposal for a new `mcpFile` JSON Schema keyword — and explores why the protocol's file handling schizophrenia (local-first…