Strapi developers often encounter the challenge of ensuring custom routes are included in the generated documentation. This step-by-step guide aims to simplify this process, ensuring a seamless integration.

1. Installing the Documentation Plugin:

• Install the Documentation plugin in your Strapi project with npm install strapi-plugin-documentation if it's not already present, you can also follow this guide from Strapi Developers Docs.

2. Adding a Custom Route:

• Reference the Strapi Custom Route Project. It includes a custom route for finding posts by slug.

3. Initial Documentation Check:

• Notice the absence of custom routes in the generated documentation before making changes.

4. Code Integration for Custom Routes:

Add the following code to the register function in the src/index.js file of your project:

register(/*{ strapi }*/) {
    if (strapi.plugin('documentation')) {
      console.log('register override')
      const override = {
        paths: {
          '/posts/slug/{slug}': {
            get: {
              operationId: 'findBySlug',
              summary: 'Find a post by slug',
              description: '',
              parameters: [
                {
                  name: 'slug',
                  in: 'path',
                  description: 'slug of post',
                  required: true,
                  schema: {
                    type: 'string',
                  },
                },
              ],
              responses: {
                200: {
                  description: 'Successful response',
                  content: {
                    'application/json': {},
                  },
                },
              },
              tags: ['Post'],
            },
          },

        },
      }
      strapi
        .plugin('documentation')
        .service('override')
        .registerOverride(override)
    }
  }

Code Breakdown:

• This script checks for the documentation plugin and then registers an override for a specific path (/posts/slug/{slug}). The get method under this path is detailed with an operationId, a summary, and other necessary configurations.

5. Server Restart:

• Restart your Strapi server to apply the changes.

6. Documentation Verification:

• The custom route for finding posts by slug should now appear in your documentation.

Conclusion: 

This guide provides a clear path for Strapi developers to include custom routes in their API documentation, ensuring a comprehensive and user-friendly API interface.