How to resolve file extensions to MIME types and reverse-map MIME types to extensions via MCP

I need an MCP server that can: (1) take a file extension or filename (e.g. "json", ".png", "report.pdf") and return the MIME content-type; (2) reverse-map a MIME content-type (e.g. "application/json", "image/svg+xml") back to the best-guess file extension. Must work via stdio with no API keys or credentials. Useful for content negotiation, file upload validation, and HTTP header generation.