File Conversion (ChangeThisFile)

File Conversion (ChangeThisFile)

Convert files between 999 conversion routes using the free ChangeThisFile service. No account or API key required. Conversions run server-side (FFmpeg, LibreOffice, Calibre, 7-Zip, sharp, Ghostscript); files are deleted within 24 hours.

Decision order

1. If ChangeThisFile MCP tools are available (changethisfile:convert_file, changethisfile:list_conversions) — use them directly. convert_file takes source_url OR base64_content + source_format, plus target_format, and returns a temporary download URL.
2. Otherwise, use the bundled script (requires network access to changethisfile.com):

scripts/​convert.sh <input-file> <target-format> [output-file]
# e.g. scripts/​convert.sh report.docx pdf
# prints the output file path on success

The script path is relative to this skill's directory. It base64-encodes the file, calls the hosted MCP endpoint over plain HTTPS, downloads the result, and writes it next to the input (or to [output-file]).

1. Remote file (you have a URL, not a local file) — skip the download/​re-upload; one curl does it:

curl -sS -X POST https://changethisfile.com/​mcp \
  -H "Content-Type: application/​json" \
  -d '{"jsonrpc":"2.0","id":1,"method":"tools/​call","params":{"name":"convert_file","arguments":{"source_url":"<FILE_URL>","target_format":"pdf"}}}'

The response text contains a download URL — fetch it with curl -o <output>.

Discovering supported routes

Ask before guessing if a conversion is exotic:

curl -sS -X POST https://changethisfile.com/​mcp \
  -H "Content-Type: application/​json" \
  -d '{"jsonrpc":"2.0","id":1,"method":"tools/​call","params":{"name":"list_conversions","arguments":{"source_format":"docx"}}}'

Omit source_format for a grouped summary of all 999 routes.

Limits and errors

• Max input: 25 MB (free path). Larger files: get a free API key (1,000 conversions/​month) at https://changethisfile.com/docs/authentication and use POST /​v1/​convert.
• Rate limit: 5 conversions/​minute per IP. On "Rate limit exceeded", wait 60 seconds and retry once.
• "Unsupported conversion: X→Y" errors list the valid targets for that source format.
• Download URLs expire after 1 hour — download immediately, then work with the local file.

Environment notes

• Needs outbound HTTPS to changethisfile.com. On claude.ai, the code-execution sandbox restricts egress by default — prefer the MCP connector there, or the user can allow the domain under Settings → Capabilities.
• Full docs: https://changethisfile.com/docs/mcp