Filetype

Tool Name: files/filetype

Determines a file's MIME type - the answer file -b --mime-type gives - detected natively from the file's first 8 KiB, so it needs no file(1) on the host. Use files/stat for size, permissions and ownership instead. Also available as the file://{path}/type resource.

Directories, devices, FIFOs, sockets and empty files get file's inode/* types; a symlink is reported as inode/symlink, not followed (as file does).
ELF binaries: application/x-executable, application/x-pie-executable, application/x-sharedlib, application/x-object, application/x-coredump.
Archives and compressors (gzip, bzip2, xz, zstd, 7z, lz4, tar, ar), .deb, .rpm, SQLite, PDF, images, audio/video and fonts the Go standard library knows, WebAssembly; #! scripts by interpreter (text/x-shellscript, text/x-script.python, text/x-perl, ...); JSON; otherwise text/plain or application/octet-stream.

file's libmagic knows far more formats (C source, makefiles, office documents, ...); for those this answers the generic text/plain or application/octet-stream. On 209 system binaries, libraries, configs and compressed docs of Ubuntu 24.04 (amd64 and arm64) the answers are identical to file's.

Example

Every example below shows the equivalent linuxctl command and the raw MCP JSON-RPC call it resolves to. The raw call always follows the same two-step pattern (see MCP API overview for the full explanation): open an SSE stream to get a one-time POST endpoint, then POST the JSON-RPC request there - the result streams back on the SSE connection.

Output captured live on an Ubuntu 24.04 host - every answer below matches file -b --mime-type there.

linuxctl

linuxctl get files filetype /usr/bin/ls

Output:

application/x-pie-executable

More answers from the same host:

/etc/hosts                                text/plain
/usr/bin/ls                               application/x-pie-executable
/usr/lib/x86_64-linux-gnu/libc.so.6       application/x-sharedlib
/usr/bin/lsb_release                      text/x-shellscript
/usr/share/doc/bash/changelog.Debian.gz   application/gzip
/etc/ssl/certs                            inode/directory
/usr/bin/python3                          inode/symlink

curl (raw MCP JSON-RPC)

# 1. Open the SSE stream (in the background) and capture the one-time POST endpoint
curl -N -s --cacert mcpd.crt -H "Authorization: Bearer $MCP_TOKEN" https://localhost:9091/sse &
# server sends: event: endpoint / data: /message?session_id=...

# 2. POST the tools/call request to that endpoint
curl -s --cacert mcpd.crt -X POST "https://localhost:9091/message?session_id=<from step 1>" \
  -H "Authorization: Bearer $MCP_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"jsonrpc": "2.0", "id": "1", "method": "tools/call", "params": {"name": "files/filetype", "arguments": {"path": "/usr/bin/ls"}}}'

# 3. The result arrives on the SSE stream opened in step 1

Response:

{
  "jsonrpc": "2.0",
  "id": "1",
  "result": {
    "content": [
      {
        "type": "text",
        "text": "application/x-pie-executable\n"
      }
    ]
  }
}

Example​

Example