How to have ChatGPT, Claude or any AI assistant send a contract for signature

An AI assistant can send a contract for signature if it can call a tool that does the sending. Add the free OpenApps MCP server to ChatGPT, Claude or your coding assistant once, then ask: "Draft a one-page NDA between me and Sam Lee, show it to me, then send it to both of us to sign." The assistant creates the document in Sign and gives you one private signing link per signer, plus an admin link for you.

There is no API key, no account and no cost. Here is how to set it up, what happens behind the scenes, and where the limits are.

Step 1: Give your assistant the tool

The OpenApps MCP server is one URL that gives an assistant every app in the store:

https://functions.openapps.xyz/apps/82875c5f2cbb469c47e29ec8/mcp

Claude Code. Run this once:

claude mcp add --transport http openapps https://functions.openapps.xyz/apps/82875c5f2cbb469c47e29ec8/mcp

Cursor, Windsurf and other editors. Add it to your MCP settings:

{"mcpServers": {"openapps": {"url": "https://functions.openapps.xyz/apps/82875c5f2cbb469c47e29ec8/mcp"}}}

ChatGPT and the Claude apps. Add a custom connector with the URL. In ChatGPT this is under developer mode. No sign-in is needed.

If your assistant cannot use MCP but can make web requests, point it at Sign's guide for assistants at sign-free.openapps.xyz/llms.txt. It lists every route of Sign's API with examples.

More on the MCP server and the other apps it covers: give your AI assistant free apps and the For AI page.

Step 2: Ask for the contract

A good request names the people and the key terms, and asks to see the text first. For example:

Draft a freelance design agreement between Sam Lee (designer) and Alex Kim (client). $1,200 on delivery, two rounds of revisions, delivery by November 15. Show me the full text. When I say go, send it to both of us for signature.

Read the draft. An assistant is not a lawyer, and you are the one agreeing to it. Sign's guide tells assistants to show the person the full text before sending, but say so in your request anyway.

Step 3: What the assistant does

When you approve, the assistant calls Sign's send_for_signature tool (or POST /documents on the API) with:

a title,
the text of the contract, as plain text or simple Markdown (headings, paragraphs and lists), up to 100,000 characters,
the signers, by name, with an optional email, up to 10 per document,
an optional message to the signers.

Sign turns the text into a PDF and adds a signature block for each signer: signature, full name and date. It answers with:

One signing link per signer. Each one is private: anyone with a signer's link can sign as that signer.
An admin link for you. It shows who has opened and signed, and the signed PDF once everyone is done.
An owner key, which lets the assistant check the status later.

Step 4: Get the links to the signers

Sign does not send email. The assistant hands you the links, and you send each person their own, by email, chat or text. If your assistant can send messages for you, it can do this step too. Either way, each signer gets only their link.

Signers open the link, read the document, agree to sign electronically, draw or type their signature and finish. No account and no app. When the last person signs, everyone can download the same signed PDF with a completion certificate: who signed, when, from which browser, and a SHA-256 fingerprint of the exact document.

Step 5: Ask how it is going

Later, ask "Has Alex signed yet?" The assistant reads the document's status with the owner key it kept: sent, completed or voided, and when each signer opened and signed. You can always check the admin link yourself.

If something changes before everyone signs, ask the assistant to void the document. The signing links stop working, and signatures already made stay on the record. Then it can send a corrected version.

Limits worth knowing

Text only through the API. The assistant creates documents from text. To send a PDF you already have, upload it yourself in the Sign web app. See how to sign a PDF for free.
Up to 10 signers per document through the API.
No bulk sending, CRM integrations or ID checks. For those, a paid tool like DocuSign or PandaDoc fits better.
Not legal advice. Electronic signatures are generally valid under the US ESIGN Act and UETA, and as simple electronic signatures under eIDAS in the EU. Some documents, such as wills and some real estate filings, need more.

Questions

Can ChatGPT send a document for signature?

Yes, if it has a tool that can. Add the OpenApps MCP server to ChatGPT as a custom connector (in developer mode), and ChatGPT can create a document in OpenApps Sign from contract text and give you a private signing link for each signer.

Do I need an API key to let my assistant use Sign?

No. OpenApps Sign's API and the OpenApps MCP server need no key and no account. The assistant gets an owner key back when it creates a document, and uses it only to check that document's status or void it.

Can my assistant send a PDF I already have?

Not through the API, which creates documents from text. To send an existing PDF, upload it in the OpenApps Sign web app, add the signers and place their fields yourself. It is free and needs no account.

Does Sign email the signers?

No. OpenApps Sign returns one private link per signer, and you or your assistant send each person their own link by email, chat or text message. Anyone with a signer's link can sign as that signer, so send it only to them.

Is a contract sent this way legally binding?

In the US, the EU and most other countries, an electronic signature is valid when the people involved intend to sign and a record is kept. OpenApps Sign records each signer's consent, when they signed, their browser and a fingerprint of the document. Some documents, such as wills, need more. This is not legal advice.