API reference

The API is a small JSON API over your account: templates (documents with their glyphs read), pacts (a document sent to people for signature) and your custom domains. It goes through the same code as the dashboard, so the same plan limits, validation and ownership rules apply.

Base URL

https://api.signwithsigil.com/v1

Every path in this reference is relative to it. v1 changes only in ways that do not break callers: new endpoints, new optional parameters, and new fields in responses. Ignore fields you do not know.

Authentication

Send your API key in Authorization: Bearer sgk_… (or X-Api-Key: sgk_…) on every call. The account needs the Pro or Business plan. See Authentication.

Requests

• JSON bodies need Content-Type: application/json and can be up to 64 KB.
• Uploads use multipart/form-data, with the document in a file part: a PDF or a Word .docx, 10 MB at most.
• Parameter and field names are snake_case.

Responses

• Everything is JSON (application/json; charset=utf-8) except the PDF downloads, and nothing is cached (Cache-Control: private, no-store).
• Fields with no value are present as null, rather than left out.
• Times are ISO 8601 in UTC, to the second: 2026-10-20T14:05:00Z.
• A delete answers 204 with no body.
• Errors are { "error": "message" } with a 4xx status. See Errors.

Ids

Templates and pacts have a uid: 8 letters and digits, such as K4TQ7MZE. They are not case-sensitive in URLs. An id that belongs to another account answers 404, the same as one that does not exist.

Paging

List pacts is paged with limit (1 to 200, default 50) and offset, and answers with total so you know when to stop. The other lists return everything.

For AI tools

GET https://api.signwithsigil.com/v1 answers with the whole reference as one Markdown document, with no key needed, so a model can read it in one request. These docs also offer every page as Markdown: add .md to its URL.

Endpoints