> ## Documentation Index
> Fetch the complete documentation index at: https://www.mintlify.com/docs/llms.txt
> Use this file to discover all available pages before exploring further.

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

> Resolve failed deployments caused by openapi, api, or asyncapi page frontmatter that lists multiple endpoints or uses a non-string value.

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:

```text theme={null}
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.

```mdx Incorrect theme={null}
---
title: "Users"
openapi: [GET /users, POST /users]
---
```

```mdx Correct theme={null}
---
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](/docs/api-playground/openapi-setup#auto-populate-api-pages).

For the full `openapi` frontmatter format, see [Document endpoints](/docs/api-playground/openapi-setup#document-endpoints).


## Related topics

- [OpenAPI setup](/docs/api-playground/openapi-setup.md)
- [Deploy at a subpath with Cloudflare Workers](/docs/deploy/cloudflare.md)
- [skill.md](/docs/ai/skillmd.md)


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