# Introduction

> Send documents for signature from your own code or from an AI assistant, with the Sigil REST API and MCP server.

Sigil turns a document into a signing workflow. Type glyphs such as `\s1\` where each person signs, send the document to them in order as a pact, and get back the signed PDF sealed with its sigil, a certificate of completion. Everything the dashboard does with a document, your code can do through the **REST API**, and an AI assistant can do through the hosted **MCP server**.

- [Quickstart](https://docs.signwithsigil.com/quickstart): Upload a document with glyphs and send it to two signers in a few calls.
- [Authentication](https://docs.signwithsigil.com/authentication): Create an API key and send it with every request.
- [API reference](https://docs.signwithsigil.com/api-reference): Every endpoint, with parameters, responses and code in three languages.
- [MCP server](https://docs.signwithsigil.com/mcp): Connect Claude, Cursor or any MCP client and send pacts by asking.

## How it works

1. **Mark a document.** Type glyphs such as `\s1\` (signer 1's signature) and `\d1\` (the date they sign) into a PDF or Word document, where each field belongs. See [Glyphs](/concepts/glyphs).
2. **Upload it as a template.** Sigil reads the glyphs and works out every field. Save it once and send it as often as you like, or upload a document for a single pact.
3. **Create a pact.** Say who signs, in what order, and who gets a copy. Sending it emails the first signer a private link.
4. **Signers sign in turn.** Each signer is invited when the one before them finishes. They agree to sign electronically, fill in their fields, and draw their signature.
5. **Get the result.** When the last signer signs, the pact is sealed: everyone receives the signed PDF and its sigil (the certificate of completion), and you can download both.

## Two ways in

| | REST API | MCP server |
|---|---|---|
| **For** | Your own code and integrations | AI assistants: Claude, Cursor, VS Code and other MCP clients |
| **Address** | `https://api.signwithsigil.com/v1` | `https://api.signwithsigil.com/mcp` |
| **Authentication** | An API key | The same API key |
| **Answers with** | JSON | Tools that return the same JSON |

Both act as the account that owns the key, under the same rules as the dashboard: the same plan limits, the same validation, the same pacts.

## Before you start

- **A Pro or Business plan.** Any account can create API keys, but the API and the MCP server answer `403` on other plans. Compare plans on the [pricing page](https://www.signwithsigil.com/pricing).
- **An API key**, made on the dashboard's [API page](https://www.signwithsigil.com/api). See [Authentication](/authentication).
- **Documents to send.** Sending a pact uses one document for every three signers. Your plan includes a monthly allowance, and you can buy packs. See [Documents and plans](/concepts/documents).

> [!TIP]
> These docs are easy for AI tools to read. Every page is also available as Markdown: add `.md` to its URL, or use **Copy page**. [llms.txt](/llms.txt) lists every page, and the API serves its own reference as Markdown at `GET https://api.signwithsigil.com/v1`, no key needed.