Images vs Text PDFs

Most real‑world faxes in 2025 are images — scans of insurance cards, lab results, driver’s licenses, or signed forms. Faxbot supports two content types only: PDF and TXT. This guide explains how to handle image content correctly and how to balance file size with HIPAA concerns.

Quick guidance

  • If you have a PDF that is a scan/photo (image‑based): send it as‑is. Use send_fax with filePath (stdio) or upload the PDF via the REST API/SDKs.
  • If you have a pure text document: paste text into a .txt file and send as TXT, or export to a text‑based PDF and send that.
  • If you have images (PNG/JPG): convert to PDF first, then send.

Conversions

  • macOS Preview: File → Export As… → Format: PDF
  • macOS CLI: sips -s format pdf "in.png" --out "out.pdf"
  • Linux: img2pdf in.png -o out.pdf or magick convert in.png out.pdf
  • Windows: open image → Print → “Microsoft Print to PDF”

MCP tooling: which option to use?

  • send_fax with filePath (stdio) — recommended for all PDFs (image or text). Sends the original file.
  • HTTP/SSE MCP transports — require base64; keep files small where possible, or prefer stdio with filePath for local usage. Node MCP JSON limit is ~16 MB; API raw limit is 10 MB.

File size and quality

  • Default limit is 10 MB (tweak under Settings → Security → Max File Size).
  • For scans, use 150–200 DPI and grayscale when possible to reduce size without losing readability.
  • For personal/one‑off use (patients): local stdio MCP with filePath avoids base64 bloat; token limits don’t apply.

HIPAA considerations

  • Healthcare providers (Covered Entities/Business Associates): use HIPAA‑aligned transports and controls.
    • Prefer OAuth‑protected SSE MCP for assistant integrations or use the REST API/SDKs directly.
    • Use HTTPS for PUBLIC_API_URL (Phaxio) and enable signature verification.
  • Patients (sending their own documents): HIPAA obligations differ; using local stdio MCP is generally acceptable because you are not a covered entity and Faxbot does not receive faxes. Providers still must protect inbound faxes on their side.

Troubleshooting

  • “Unsupported file type”: only PDF and TXT are accepted. Convert images to PDF.
  • Shell path issues with spaces/odd characters: quote the entire path or rename using a wildcard (e.g., cp Screenshot*.pdf card.pdf).

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