Fix "frontmatter must be a single endpoint string" deploy errors

Each MDX endpoint page in Mintlify documents exactly one endpoint. The openapi, api, and asyncapi frontmatter fields must each be a single string. If any page sets one of these fields to a list, a number, or another non-string value, Mintlify fails the deployment with this message:

Page api, openapi, or asyncapi frontmatter must be a single endpoint string. Deployment not updated

Mintlify does not publish any changes from a failed deployment. Your live site keeps serving the last successful deployment until you fix the page. The error for the individual page starts with Invalid "<field>" frontmatter at path. It names the page path and the type of value Mintlify received, such as received an array.

Common causes

Listing several endpoints in one field, such as openapi: [GET /users, POST /users].
Writing the value as a YAML list on separate lines that start with -.
Using a value that YAML parses as a number or boolean instead of a string.

Fix the frontmatter

Set the field to one endpoint string. Wrap the value in quotes so YAML always parses it as a string.

Incorrect

---
title: "Users"
openapi: [GET /users, POST /users]
---

Correct

---
title: "List users"
openapi: "GET /users"
---

To document more than one endpoint, create a separate page for each endpoint. You can also let Mintlify generate one page per operation from your spec. See Auto-populate API pages. For the full openapi frontmatter format, see Document endpoints.

​Common causes

​Fix the frontmatter

Common causes

Fix the frontmatter