# Lint Open-RPC with Redocly CLI

Experimental Open-RPC support
This feature is at an early stage, please use with caution and send us lots of feedback!

In addition to providing lint functionality for multiple OpenAPI formats, Redocly CLI also has support for Open-RPC.
Redocly CLI supports the following linting approaches with Open-RPC documents:

- Open-RPC document validation.
- Supported versions:
  - [Open-RPC 1.x](https://spec.open-rpc.org/)
- Built-in rules for checking common standards requirements (see the [list of Open-RPC rules](#open-rpc-rules)).
- [Configurable rules](/docs/cli/rules/configurable-rules) so that you can build your own rules following common patterns
- [Custom plugins](/docs/cli/custom-plugins) for advanced users that need additional functionality


## Lint an existing Open-RPC file

Redocly CLI takes its settings from a `redocly.yaml` configuration file.
Below is an example of a simple configuration file for validating an Open-RPC file is in the expected format:


```yaml
rules:
  struct: error
```

The empty `extends` element instructs Redocly CLI not to use any existing rulesets, but to display an error if the `struct` rule finds any problem.
This rule checks that the document structure matches the Open-RPC specification.

With this configuration file, and your Open-RPC description file, run the linting command:


```sh
redocly lint open-rpc.json
```

The output describes any structural problems with the document, or reports that it is valid.

## Open-RPC rules

To expand the linting checks for an Open-RPC description, start by enabling some of the built-in rules.
The currently supported rules are:

- `no-unresolved-refs`: Every `$ref` must exist.
- `no-unused-components`: All components must be used.
- `spec-no-duplicated-method-params`: The list of parameters must not include duplicated parameters.
- `spec-no-required-params-after-optional`: Required parameters must be positioned before optional parameters.
- `info-contact`: Contact section is defined under `info`.
- `info-license`: License section is defined under `info`.


We expect the list to expand over time, so keep checking back - and let us know if you have any requests by [opening an issue on the GitHub repo](https://github.com/Redocly/redocly-cli/issues).

To use a rule in your own linting setup, add the rule name to the `rules` configuration section, and declare the severity level (either `error`, `warn` or `off`).
Here's an example of a rules block where a missing contact section causes a warning, and a tag without a description triggers an error:


```yaml
rules:
  info-contact: warn
  info-license: error
```

Pick and mix the available rules until you have the setup that fits your situation.

## Configurable rule example

Redocly CLI also offers [configurable rules](/docs/cli/rules/configurable-rules) that allow you to set assertions about the API description being linted. This functionality works for Open-RPC too.
The following example shows a configurable rule that displays a warning if the `title` field is not present in the `info` block:


```yaml
rules:
  rule/info-title:
    subject:
      type: Info
      property: title
    assertions:
      defined: true
    severity: warn
```

With the extensive configurable rules options available, there are many opportunities to make sure that your Open-RPC spec conforms with expectations. We'd also love to see what you're building - it helps us know how things are going!

Custom plugins
To create your own plugins, see the [custom plugins documentation](/docs/cli/custom-plugins).