diff --git a/__tests__/utils/index.js b/__tests__/utils/index.js
index 7c0c46befb..6b6bc931b1 100644
--- a/__tests__/utils/index.js
+++ b/__tests__/utils/index.js
@@ -41,10 +41,13 @@ function mkdtempSync () {
  * @param {string} prototypePath
  * @param {Object} [options]
  * @param {string} [options.kitPath] - Path to the kit to use when creating prototype, if not provided uses mkReleaseArchive
- * @param {bool} [options.allowTracking] - If undefined no usage-data-config.json is created,
+ * @param {boolean} [options.overwrite] - Allow existing prototype to be overwritten (optional)
+ * @param {boolean} [options.allowTracking] - If undefined no usage-data-config.json is created (optional),
  *                                         if true a usage-data-config.json is created allowing tracking,
  *                                         if false a usage-data-config.json is crated disallowing tracking
- * @returns {void}
+ * @param {boolean} [options.npmInstallLinks] - Set value for npm config install-links (optional)
+ * @param {string} [options.commandLineParameters] - Command line parameters (optional)
+ * @returns {Promise<void>}
  */
 async function mkPrototype (prototypePath, {
   kitPath,
diff --git a/bin/utils/argv-parser.js b/bin/utils/argv-parser.js
index 00f8a04497..e764ae4127 100644
--- a/bin/utils/argv-parser.js
+++ b/bin/utils/argv-parser.js
@@ -1,11 +1,23 @@
+/**
+ *
+ * @param {NodeJS.Process["argv"]} argvInput
+ * @param {{ booleans?: string[] }} config
+ */
 function parse (argvInput, config = {}) {
   const args = [...argvInput].splice(2)
-  const options = {}
-  const paths = []
+  const options = /** @type {Object<string, string | boolean>} */ ({})
+  const paths = /** @type {string[]} */ ([])
   const booleanOptions = config.booleans || []
+
+  /** @type {string | undefined} */
   let command
+
+  /** @type {{ option: string } | undefined} */
   let contextFromPrevious
 
+  /**
+   * @param {string} unprocessed
+   */
   const processOptionName = (unprocessed) => {
     if (unprocessed.startsWith('--')) {
       return unprocessed.substring(2)
@@ -15,6 +27,9 @@ function parse (argvInput, config = {}) {
     }
   }
 
+  /**
+   * @param {string} arg
+   */
   const prepareArg = (arg) => {
     if ((arg.startsWith('"') && arg.endsWith('"')) || (arg.startsWith('\'') && arg.endsWith('\''))) {
       return arg.substring(1, arg.length - 1)
@@ -64,3 +79,7 @@ function parse (argvInput, config = {}) {
 module.exports = {
   parse
 }
+
+/**
+ * @typedef {ReturnType<typeof parse>} ArgvParsed
+ */
diff --git a/lib/govukFrontendPaths.js b/lib/govukFrontendPaths.js
index 000ba2f51e..34cb546d31 100644
--- a/lib/govukFrontendPaths.js
+++ b/lib/govukFrontendPaths.js
@@ -47,5 +47,5 @@ module.exports = {
  * @property {string} baseDir - GOV.UK Frontend directory path
  * @property {URL["pathname"]} includePath - URL path to GOV.UK Frontend includes
  * @property {URL["pathname"]} assetPath - URL path to GOV.UK Frontend assets
- * @property {{ [key: string]: unknown }} config - GOV.UK Frontend plugin config
+ * @property {import('./plugins/plugins').ConfigManifest} config - GOV.UK Frontend plugin config
  */
diff --git a/lib/plugins/plugin-validator.js b/lib/plugins/plugin-validator.js
index 2a392608d0..1564180b60 100644
--- a/lib/plugins/plugin-validator.js
+++ b/lib/plugins/plugin-validator.js
@@ -21,18 +21,32 @@ const knownKeys = [
   'meta'
 ]
 
+/**
+ * @param {string} executionPath
+ * @param {string} pathToValidate
+ * @param {string} key
+ */
 function checkPathExists (executionPath, pathToValidate, key) {
   const absolutePathToValidate = path.join(executionPath, pathToValidate)
   if (!fse.existsSync(absolutePathToValidate)) errors.push(`In section ${key}, the path '${pathToValidate}' does not exist`)
 }
 
+/**
+ * @param {string} executionPath
+ * @param {string} nunjucksFileName
+ * @param {string | string[]} nunjucksPaths
+ */
 function checkNunjucksMacroExists (executionPath, nunjucksFileName, nunjucksPaths) {
   // set up a flag for the existance of a nunjucks path
   let nunjucksPathExists = false
 
-  if (nunjucksPaths === undefined) {
-    // Check if the nunjucksMacros are at the root level of the project
-    if (fse.existsSync(path.join(executionPath, nunjucksFileName))) nunjucksPathExists = true
+  if (!nunjucksPaths || typeof nunjucksPaths === 'string') {
+    const pathToCheck = typeof nunjucksPaths === 'string'
+      ? path.join(executionPath, nunjucksPaths, nunjucksFileName)
+      : path.join(executionPath, nunjucksFileName) // root level
+
+    // Check if the nunjucksMacros are at a single path in the project
+    if (fse.existsSync(pathToCheck)) nunjucksPathExists = true
   } else {
     // Combine the file path name for each nunjucks path and check if any one of them exists
     for (const nunjucksPath of nunjucksPaths) {
@@ -47,14 +61,22 @@ function checkNunjucksMacroExists (executionPath, nunjucksFileName, nunjucksPath
   if (!nunjucksPathExists) errors.push(`The nunjucks file '${nunjucksFileName}' does not exist`)
 }
 
+/**
+ * @param {string[]} invalidKeys
+ */
 function reportInvalidKeys (invalidKeys) {
   errors.push(`The following invalid keys exist in your config: ${invalidKeys}`)
 }
 
+/**
+ * @param {ConfigManifest} pluginConfig
+ * @param {ArgvParsed} argv
+ * @returns {ConfigManifest}
+ */
 function validateConfigKeys (pluginConfig, argv) {
   console.log('Config file exists, validating contents.')
-  const keysToAllowThrough = argv?.options?.keysToIgnoreIfUnknown || ''
-  const allowedKeys = knownKeys.concat(keysToAllowThrough.split(',').filter(key => !!key))
+  const keysToAllowThrough = `${argv?.options?.keysToIgnoreIfUnknown || ''}`
+  const allowedKeys = [...knownKeys, ...keysToAllowThrough.split(',').filter(key => !!key)]
   const invalidKeys = []
 
   const validKeysPluginConfig = Object.fromEntries(Object.entries(pluginConfig).filter(([key]) => {
@@ -73,6 +95,12 @@ function validateConfigKeys (pluginConfig, argv) {
   return validKeysPluginConfig
 }
 
+/**
+ * @template {ConfigEntry | ConfigURLs} ObjectType
+ * @param {ObjectType} objectToEvaluate
+ * @param {string[]} allowedKeys
+ * @param {string} [keyPath]
+ */
 function reportUnknownKeys (objectToEvaluate, allowedKeys, keyPath) {
   const invalidMetaUrlKeys = Object.keys(objectToEvaluate).filter(key => !allowedKeys.includes(key)).map(key => `${keyPath || ''}${key}`)
   if (invalidMetaUrlKeys.length > 0) {
@@ -80,6 +108,9 @@ function reportUnknownKeys (objectToEvaluate, allowedKeys, keyPath) {
   }
 }
 
+/**
+ * @param {string} url
+ */
 function isValidUrl (url) {
   if (!url.startsWith('https://') && !url.startsWith('http://')) {
     return false
@@ -90,6 +121,9 @@ function isValidUrl (url) {
   return true
 }
 
+/**
+ * @param {ConfigURLs} [metaUrls]
+ */
 function validateMetaUrls (metaUrls) {
   if (typeof metaUrls === 'undefined') {
     return
@@ -121,6 +155,9 @@ function validateMetaUrls (metaUrls) {
   })
 }
 
+/**
+ * @param {ConfigEntry} meta
+ */
 function validateMeta (meta) {
   const metaKeys = ['urls', 'description']
 
@@ -142,6 +179,10 @@ function validateMeta (meta) {
   validateMetaUrls(meta.urls)
 }
 
+/**
+ * @param {string} key
+ * @param {ConfigEntry} configEntry
+ */
 function validatePluginDependency (key, configEntry) {
   if (typeof configEntry !== 'object' || Array.isArray(configEntry)) {
     return
@@ -165,16 +206,20 @@ function validatePluginDependency (key, configEntry) {
   }
 }
 
+/**
+ * @param {ConfigManifest} pluginConfig
+ * @param {string} executionPath
+ */
 function validateConfigurationValues (pluginConfig, executionPath) {
   console.log('Validating whether config paths meet criteria.')
   const keysToValidate = Object.keys(pluginConfig)
 
   keysToValidate.forEach(key => {
-    // Convert any strings to an array so that they can be processed
-    let criteriaConfig = pluginConfig[key]
-    if (!Array.isArray(criteriaConfig)) {
-      criteriaConfig = [criteriaConfig]
-    }
+    /**
+     * Convert any strings to an array so that they can be processed
+     * @type {ConfigEntry[]}
+     */
+    const criteriaConfig = [pluginConfig[key]].flat()
 
     criteriaConfig.forEach((configEntry) => {
       try {
@@ -203,11 +248,16 @@ function validateConfigurationValues (pluginConfig, executionPath) {
   })
 }
 
+/**
+ * @param {string} executionPath
+ * @param {ArgvParsed} argv
+ */
 async function validatePlugin (executionPath, argv) {
   console.log()
   const configPath = path.join(executionPath, 'govuk-prototype-kit.config.json')
   await fse.exists(configPath).then(exists => {
     if (exists) {
+      /** @type {ConfigManifest | undefined} */
       let pluginConfig
       try {
         pluginConfig = JSON.parse(fs.readFileSync(configPath, 'utf8'))
@@ -267,3 +317,10 @@ module.exports = {
   validateMeta,
   validatePluginDependency
 }
+
+/**
+ * @typedef {import('./plugins').ConfigManifest} ConfigManifest
+ * @typedef {import('./plugins').ConfigURLs} ConfigURLs
+ * @typedef {import('./plugins').ConfigEntry} ConfigEntry
+ * @typedef {import('../../bin/utils/argv-parser').ArgvParsed} ArgvParsed
+ */
diff --git a/lib/plugins/plugins.js b/lib/plugins/plugins.js
index f8523286cc..b94d69641d 100644
--- a/lib/plugins/plugins.js
+++ b/lib/plugins/plugins.js
@@ -9,37 +9,8 @@
  * The kit code retrieves the paths as and when needed; this module just
  * contains the code to find and list paths defined by plugins.
  *
- * A schema for an example manifest file follows:
- *
- *     // govuk-prototype-kit.config.json
- *     {
- *       "assets": string | string[],
- *       "importNunjucksMacrosInto": string | string[],
- *       "meta": {
- *         "description": string,
- *         "urls": {
- *           "documentation": string,
- *           "versionHistory": string,
- *           "releaseNotes": string
- *         }
- *       },
- *       "nunjucksMacros": {"importFrom": string, "macroName": string} | {"importFrom": string, "macroName": string}[],
- *       "nunjucksPaths": string | string[],
- *       "nunjucksFilters": string | string[],
- *       "nunjucksFunctions": string | string[],
- *       "pluginDependencies": [{"packageName": string, "minVersion": string, "maxVersion": string}],
- *       "sass": string | string[],
- *       "scripts": string | string[] | {"path": string, "type": string} | {"path": string, "type": string}[],
- *       "stylesheets": string | string[],
- *       "templates": {
- *         "name": string,
- *         "path": string,
- *         "type": string
- *       }[]
- *     }
- *
- * Note that all the top-level keys are optional.
- *
+ * See JSDoc `ConfigManifest` for example govuk-prototype-kit.json manifiest
+ * {@link ConfigManifest}
  */
 
 // core dependencies
@@ -313,8 +284,9 @@ const getByType = type => getList(type)
 
 /**
  * Gets public urls for all plugins of type
- * @param {string} listType - (scripts, stylesheets, nunjucks etc)
- * @return {string[]} A list of urls
+ * @template {'assets' | 'scripts' | 'stylesheets'} ListType
+ * @param {ListType} listType - (scripts, stylesheets, nunjucks etc)
+ * @return {ListType extends 'scripts' ? AppScript[] | string[] : string[]} A list of urls or script objects
  */
 const getPublicUrls = listType => getList(listType).map(({ packageName, item }) => {
   // item will either be the plugin path or will be an object containing the plugin path within the src property
@@ -343,8 +315,8 @@ const getPublicUrlAndFileSystemPaths = type => getList(type).map(getPublicUrlAnd
 
 /**
  * This is used in the views to output links and scripts for each file
- * @param {{scripts: string[], stylesheets: string[]}} additionalConfig
- * @return {{scripts: {src: string, type: string}[], stylesheets: string[]}} Returns an object containing two keys(scripts & stylesheets),
+ * @param {Partial<{ scripts: (AppScript | string)[], stylesheets: string[] }>} [additionalConfig]
+ * @return {{ scripts: AppScript[], stylesheets: string[] }} Returns an object containing two keys(scripts & stylesheets),
  *   each item contains an array of full paths to specific files.
  */
 function getAppConfig (additionalConfig) {
@@ -385,3 +357,91 @@ const self = module.exports = {
   setPluginsByType,
   watchPlugins
 }
+
+/**
+ * Prototype Kit plugin config
+ *
+ * Schema for govuk-prototype-kit.json manifiest
+ * Note: All top-level keys are optional
+ *
+ * @typedef {object} ConfigManifest
+ * @property {string | string[]} [assets] - Static asset paths
+ * @property {string | string[]} [importNunjucksMacrosInto] - Templates to import Nunjucks macros into
+ * @property {string | string[]} [nunjucksPaths] - Nunjucks paths
+ * @property {ConfigNunjucksMacro[]} [nunjucksMacros] - Nunjucks macros to include
+ * @property {string | string[]} [nunjucksFilters] - Nunjucks filters to include
+ * @property {string | string[]} [nunjucksFunctions] - Nunjucks functions to include
+ * @property {string | string[]} [sass] - Sass stylesheets to compile
+ * @property {ConfigScript[] | string[]} [scripts] - JavaScripts to serve
+ * @property {string | string[]} [stylesheets] - Stylesheets to serve
+ * @property {ConfigTemplate[]} [templates] - Templates available
+ * @property {ConfigDependency[]} [pluginDependencies] - Plugin dependencies
+ * @property {ConfigMeta} [meta] - Plugin metadata
+ */
+
+/**
+ * Prototype Kit plugin Nunjucks macro
+ *
+ * @typedef {object} ConfigNunjucksMacro
+ * @property {string} macroName - Nunjucks macro name
+ * @property {string} importFrom - Path to import Nunjucks macro from
+ */
+
+/**
+ * Prototype Kit plugin script
+ *
+ * @typedef {object} ConfigScript
+ * @property {string} path - Path to script
+ * @property {string} [type] - Type attribute for script
+ */
+
+/**
+ * Prototype Kit plugin template
+ *
+ * @typedef {object} ConfigTemplate
+ * @property {string} name - Template name
+ * @property {string} path - Path to template
+ * @property {string} type - Template type
+ */
+
+/**
+ * Prototype Kit plugin dependency
+ *
+ * @typedef {object} ConfigDependency
+ * @property {string} packageName - Package name
+ * @property {string} minVersion - Package minimum version
+ * @property {string} maxVersion - Package maximum version
+ */
+
+/**
+ * Prototype Kit plugin metadata
+ *
+ * @typedef {object} ConfigMeta
+ * @property {string} description - Plugin description
+ * @property {ConfigURLs} urls - Plugin URLs
+ */
+
+/**
+ * Prototype Kit plugin URLs
+ *
+ * @typedef {object} ConfigURLs
+ * @property {string} documentation - Documentation URL
+ * @property {string} releaseNotes - Release notes URL
+ * @property {string} versionHistory - Version history URL
+ */
+
+/**
+ * Prototype Kit application script
+ *
+ * Plugin {@link ConfigScript} objects use `path` keys but
+ * these keys are renamed to `src` once imported into the
+ * application by `plugins.getAppConfig()`
+ *
+ * @typedef {object} AppScript
+ * @property {string} src - Path to script
+ * @property {string} [type] - Type attribute for script
+ */
+
+/**
+ * @typedef {string | string[] | ConfigNunjucksMacro | ConfigScript | ConfigTemplate | ConfigDependency | ConfigMeta} ConfigEntry
+ */
diff --git a/lib/utils/index.js b/lib/utils/index.js
index 353b3bea58..313a9a248e 100644
--- a/lib/utils/index.js
+++ b/lib/utils/index.js
@@ -35,6 +35,12 @@ marked.use({
   }
 })
 
+/**
+ * Application scripts passed into `plugins.getAppConfig()` where
+ * plugin {@link ConfigScript} is converted to {@link AppScript}
+ *
+ * @type {(AppScript | string)[]}
+ */
 const scripts = []
 if (existsSync(path.join(projectDir, 'app', 'assets', 'javascripts', 'application.js'))) {
   scripts.push({
@@ -312,3 +318,8 @@ module.exports = {
   sortByObjectKey,
   hasNewVersion
 }
+
+/**
+ * @typedef {import('../plugins/plugins').AppScript} AppScript
+ * @typedef {import('../plugins/plugins').ConfigScript} ConfigScript
+ */