Codex can use DearFax’s MCP tools to prepare a fax, request your confirmation, and check delivery. This is useful when you have already created a letter, report, or other document in a coding workspace and need to send the finished pages to a fax number.
Connect Codex to DearFax
You need enabled DearFax MCP access and an approved OAuth connection. The commands below use the Codex CLI; other Codex surfaces may expose MCP settings in their interface.
codex mcp add dearfax --url https://app.dearfax.com/api/mcp
codex mcp login dearfax
Complete sign-in in the browser and approve only the access your task needs. If your connection requires a pre-registered client ID, use the registration details supplied for that connection; do not invent a client ID or callback URL. OpenAI’s MCP documentation explains client registration and configuration.
Ask Codex to list your DearFax workspaces. Choose one explicitly and keep tool approvals enabled. If connection setup is unavailable, use the DearFax browser workflow with the same finished document.
Export and inspect the finished document
Have Codex save a final PDF, then open it yourself. Check pagination, signatures, small text, and any values generated from source data. A correct source file does not guarantee that its exported pages look right.
Codex’s access to your local filesystem does not give DearFax access to it. Passing a path such as ./letter.pdf to the remote attachment tool is not supported. Use a supported file-transfer mechanism or a short-lived direct HTTPS link from an approved document system. If neither is available, upload the PDF through the saved draft’s authenticated editor link.
Do not commit the document, publish it on a website, or expose a development server just to make it downloadable. DearFax accepts supported PDFs and images up to 20 MB each, with a maximum of 350 pages per fax including the cover.
Ask Codex to prepare a fax
Provide the recipient’s verified US or Canadian fax number and identify the document precisely:
Prepare a fax in [workspace name] for [recipient name] at [verified fax number]. Use the final PDF at [supported document link]. Add [cover message]. Show the saved fax review and wait for my confirmation before sending.
Codex should return the actual draft review, not merely a plan to send. Check the attached filenames, page count, destination, cover message, and sending number. If you uploaded through the browser, ask Codex to review the updated draft again.
A draft change invalidates the previous review. A review also expires after ten minutes. Request a fresh review whenever either applies, then explicitly confirm the send.
Follow the same fax through delivery
Record the fax ID returned by DearFax. Ask Codex for that fax’s status and, once Delivered is confirmed, its delivery receipt. Queued means accepted for sending; it does not mean the recipient’s fax system has received the pages.
If an action times out, have Codex inspect the existing fax before retrying. For programmatic draft preparation, retain the same request ID and identical arguments after an uncertain response rather than generating a new request.
The connection uses your existing workspace sending eligibility and page allowance. It does not bypass document limits or purchase more capacity.
Keep recurring workflows explicit
A script that prepares a fax is not permission to send future documents automatically. Retain the review and explicit confirmation step for every outbound fax. For event-driven receiving, a persistent runner can retrieve incoming documents and process them separately; see how to turn faxed purchase orders into draft orders.
The DearFax Codex page provides the integration overview. Preview testing establishes only the tested flows; it does not guarantee access in every Codex account or production environment.