diff --git a/.gitignore b/.gitignore
index a547bf3..d056240 100644
--- a/.gitignore
+++ b/.gitignore
@@ -10,6 +10,7 @@ lerna-debug.log*
 node_modules
 dist
 dist-ssr
+docs
 *.local
 
 # Editor directories and files
diff --git a/package.json b/package.json
index e90e2db..3fd23dd 100644
--- a/package.json
+++ b/package.json
@@ -54,6 +54,7 @@
     "globals": "^15.14.0",
     "husky": "^9.1.7",
     "prettier": "^3.4.2",
+    "typedoc": "^0.27.6",
     "typescript": "^5.7.2",
     "typescript-eslint": "^8.18.2",
     "vite": "^6.0.6",
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index 539f091..15bb864 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -38,6 +38,9 @@ importers:
       prettier:
         specifier: ^3.4.2
         version: 3.4.2
+      typedoc:
+        specifier: ^0.27.6
+        version: 0.27.6(typescript@5.7.2)
       typescript:
         specifier: ^5.7.2
         version: 5.7.2
@@ -46,7 +49,7 @@ importers:
         version: 8.18.2(eslint@9.17.0(jiti@2.4.2))(typescript@5.7.2)
       vite:
         specifier: ^6.0.6
-        version: 6.0.6(@types/node@22.10.2)(jiti@2.4.2)
+        version: 6.0.6(@types/node@22.10.2)(jiti@2.4.2)(yaml@2.6.1)
       vitest:
         specifier: ^0.34.6
         version: 0.34.6
@@ -459,6 +462,9 @@ packages:
     resolution: {integrity: sha512-zSkKow6H5Kdm0ZUQUB2kV5JIXqoG0+uH5YADhaEHswm664N9Db8dXSi0nMJpacpMf+MyyglF1vnZohpEg5yUtg==}
     engines: {node: ^18.18.0 || ^20.9.0 || >=21.1.0}
 
+  '@gerrit0/mini-shiki@1.24.4':
+    resolution: {integrity: sha512-YEHW1QeAg6UmxEmswiQbOVEg1CW22b1XUD/lNTliOsu0LD0wqoyleFMnmbTp697QE0pcadQiR5cVtbbAPncvpw==}
+
   '@humanfs/core@0.19.1':
     resolution: {integrity: sha512-5DyQ4+1JEUzejeK1JGICcideyfUbGixgS9jNgex5nqkW+cY7WZhxBigmieN5Qnw9ZosSNVC9KQKyb+GUaGyKUA==}
     engines: {node: '>=18.18.0'}
@@ -612,6 +618,15 @@ packages:
     cpu: [x64]
     os: [win32]
 
+  '@shikijs/engine-oniguruma@1.24.4':
+    resolution: {integrity: sha512-Do2ry6flp2HWdvpj2XOwwa0ljZBRy15HKZITzPcNIBOGSeprnA8gOooA/bLsSPuy8aJBa+Q/r34dMmC3KNL/zw==}
+
+  '@shikijs/types@1.24.4':
+    resolution: {integrity: sha512-0r0XU7Eaow0PuDxuWC1bVqmWCgm3XqizIaT7SM42K03vc69LGooT0U8ccSR44xP/hGlNx4FKhtYpV+BU6aaKAA==}
+
+  '@shikijs/vscode-textmate@9.3.1':
+    resolution: {integrity: sha512-79QfK1393x9Ho60QFyLti+QfdJzRQCVLFb97kOIV7Eo9vQU/roINgk7m24uv0a7AUvN//RDH36FLjjK48v0s9g==}
+
   '@sinclair/typebox@0.27.8':
     resolution: {integrity: sha512-+Fj43pSMwJs4KRrH/938Uf+uAELIgVBmQzg/q1YG10djyfA3TnrU8N8XzqCh/okZdszqBQTZf96idMfE5lnwTA==}
 
@@ -627,6 +642,9 @@ packages:
   '@types/estree@1.0.6':
     resolution: {integrity: sha512-AYnb1nQyY49te+VRAVgmzfcgjYS91mY5P0TKUDCLEM+gNnA+3T6rWITXRLYCpahpqSQbN5cE+gHpnPyXjHWxcw==}
 
+  '@types/hast@3.0.4':
+    resolution: {integrity: sha512-WPs+bbQw5aCj+x6laNGWLH3wviHtoCv/P3+otBhbOhJgG8qtpdAMlTCxLtsTWA7LH1Oh/bFCHsBn0TPS5m30EQ==}
+
   '@types/istanbul-lib-coverage@2.0.6':
     resolution: {integrity: sha512-2QF/t/auWm0lsy8XtKVPG19v3sSOQlJe/YHZgfjb/KBBHOGSV+J2q/S671rcq9uTBrLAXmZpqJiaQbMT+zNU1w==}
 
@@ -636,6 +654,9 @@ packages:
   '@types/node@22.10.2':
     resolution: {integrity: sha512-Xxr6BBRCAOQixvonOye19wnzyDiUtTeqldOOmj3CkeblonbccA12PFwlufvRdrpjXxqnmUaeiU5EOA+7s5diUQ==}
 
+  '@types/unist@3.0.3':
+    resolution: {integrity: sha512-ko/gIFJRv177XgZsZcBwnqJN5x/Gien8qNOn0D5bQU/zAzVf9Zt3BlcUiLqhV9y4ARk0GbT3tnUiPNgnTXzc/Q==}
+
   '@typescript-eslint/eslint-plugin@8.18.2':
     resolution: {integrity: sha512-adig4SzPLjeQ0Tm+jvsozSGiCliI2ajeURDGHjZ2llnA+A67HihCQ+a3amtPhUakd1GlwHxSRvzOZktbEvhPPg==}
     engines: {node: ^18.18.0 || ^20.9.0 || >=21.1.0}
@@ -872,6 +893,10 @@ packages:
   emoji-regex@8.0.0:
     resolution: {integrity: sha512-MSjYzcWNOA0ewAHpz0MxpYFvwg6yjy1NG3xteoqz644VCo/RPgnr1/GGt+ic3iJTzQ8Eu3TdM14SawnVUmGE6A==}
 
+  entities@4.5.0:
+    resolution: {integrity: sha512-V0hjH4dGPh9Ao5p0MoRY6BVqtwCjhz6vI5LT8AJ55H+4g9/4vbHx1I54fS0XuclLhDHArPQCiMjDxjaL8fPxhw==}
+    engines: {node: '>=0.12'}
+
   env-paths@2.2.1:
     resolution: {integrity: sha512-+h1lkLKhZMTYjog1VEpJNG7NZJWcuc2DDk/qsqSTRRCOXiLjeQ1d1/udrUGhqMxUgAlwKNZ0cf2uqan5GLuS2A==}
     engines: {node: '>=6'}
@@ -1158,6 +1183,9 @@ packages:
   lines-and-columns@1.2.4:
     resolution: {integrity: sha512-7ylylesZQ/PV29jhEDl3Ufjo6ZX7gCqJr5F7PKrqc93v7fzSymt1BpwEU8nAUXs8qzzvqhbjhK5QZg6Mt/HkBg==}
 
+  linkify-it@5.0.0:
+    resolution: {integrity: sha512-5aHCbzQRADcdP+ATqnDuhhJ/MRIqDkZX5pyjFHRRysS8vZ5AbqGEoFIb6pYHPZ+L/OC2Lc+xT8uHVVR5CAK/wQ==}
+
   local-pkg@0.4.3:
     resolution: {integrity: sha512-SFppqq5p42fe2qcZQqqEOiVRXl+WCP1MdT6k7BDEW1j++sp5fIY+/fdRQitvKgB5BrBcmrs5m/L0v2FrU5MY1g==}
     engines: {node: '>=14'}
@@ -1200,6 +1228,9 @@ packages:
   loupe@2.3.7:
     resolution: {integrity: sha512-zSMINGVYkdpYSOBmLi0D1Uo7JU9nVdQKrHxC8eYlV+9YKK9WePqAlL7lSlorG/U2Fw1w0hTBmaa/jrQ3UbPHtA==}
 
+  lunr@2.3.9:
+    resolution: {integrity: sha512-zTU3DaZaF3Rt9rhN3uBMGQD3dD2/vFQqnvZCDv4dl5iOzq2IZQqTxu90r4E5J+nP70J3ilqVCrbho2eWaeW8Ow==}
+
   magic-string@0.30.17:
     resolution: {integrity: sha512-sNPKHvyjVf7gyjwS4xGTaW/mCnF8wnjtifKBEhxfZ7E/S8tQ0rssrwGNn6q8JH/ohItJfSQp9mBtQYuTlH5QnA==}
 
@@ -1207,6 +1238,13 @@ packages:
     resolution: {integrity: sha512-hXdUTZYIVOt1Ex//jAQi+wTZZpUpwBj/0QsOzqegb3rGMMeJiSEu5xLHnYfBrRV4RH2+OCSOO95Is/7x1WJ4bw==}
     engines: {node: '>=10'}
 
+  markdown-it@14.1.0:
+    resolution: {integrity: sha512-a54IwgWPaeBCAAsv13YgmALOF1elABB08FxO9i+r4VFk5Vl4pKokRPeX8u5TCgSsPi6ec1otfLjdOpVcgbpshg==}
+    hasBin: true
+
+  mdurl@2.0.0:
+    resolution: {integrity: sha512-Lf+9+2r+Tdp5wXDXC4PcIBjTDtq4UKjCPMQhKIuzpJNW0b96kVqSwW0bT7FhRSfmAiFYgP+SCRvdrDozfh0U5w==}
+
   meow@12.1.1:
     resolution: {integrity: sha512-BhXM0Au22RwUneMPwSCnyhTOizdWoIEPU9sp0Aqa1PnDMR5Wv2FGXYDjuzJEIX+Eo2Rb8xuYe5jrnm5QowQFkw==}
     engines: {node: '>=16.10'}
@@ -1323,6 +1361,10 @@ packages:
     resolution: {integrity: sha512-Pdlw/oPxN+aXdmM9R00JVC9WVFoCLTKJvDVLgmJ+qAffBMxsV85l/Lu7sNx4zSzPyoL2euImuEwHhOXdEgNFZQ==}
     engines: {node: ^14.15.0 || ^16.10.0 || >=18.0.0}
 
+  punycode.js@2.3.1:
+    resolution: {integrity: sha512-uxFIHU0YlHYhDQtV4R9J6a52SLx28BCjT+4ieh7IGbgwVJWO+km431c4yRlREUAsAmt/uMjQUyQHNEPf0M39CA==}
+    engines: {node: '>=6'}
+
   punycode@2.3.1:
     resolution: {integrity: sha512-vYt7UD1U9Wg6138shLtLOvdAu+8DsC/ilFtEVHcH+wydcSpNE20AfSOduf6MkRFahL5FY7X1oU7nKVZFtfq8Fg==}
     engines: {node: '>=6'}
@@ -1457,6 +1499,13 @@ packages:
     resolution: {integrity: sha512-Acylog8/luQ8L7il+geoSxhEkazvkslg7PSNKOX59mbB9cOveP5aq9h74Y7YU8yDpJwetzQQrfIwtf4Wp4LKcw==}
     engines: {node: '>=4'}
 
+  typedoc@0.27.6:
+    resolution: {integrity: sha512-oBFRoh2Px6jFx366db0lLlihcalq/JzyCVp7Vaq1yphL/tbgx2e+bkpkCgJPunaPvPwoTOXSwasfklWHm7GfAw==}
+    engines: {node: '>= 18'}
+    hasBin: true
+    peerDependencies:
+      typescript: 5.0.x || 5.1.x || 5.2.x || 5.3.x || 5.4.x || 5.5.x || 5.6.x || 5.7.x
+
   typescript-eslint@8.18.2:
     resolution: {integrity: sha512-KuXezG6jHkvC3MvizeXgupZzaG5wjhU3yE8E7e6viOvAvD9xAWYp8/vy0WULTGe9DYDWcQu7aW03YIV3mSitrQ==}
     engines: {node: ^18.18.0 || ^20.9.0 || >=21.1.0}
@@ -1469,6 +1518,9 @@ packages:
     engines: {node: '>=14.17'}
     hasBin: true
 
+  uc.micro@2.1.0:
+    resolution: {integrity: sha512-ARDJmphmdvUk6Glw7y9DQ2bFkKBHwQHLi2lsaH6PPmz/Ka9sFOBsBluozhDltWmnv9u/cF6Rt87znRTPV+yp/A==}
+
   ufo@1.5.4:
     resolution: {integrity: sha512-UsUk3byDzKd04EyoZ7U4DOlxQaD14JUKQl6/P7wiX4FNvUfm3XL246n9W5AmqwW5RSFJ27NAuM0iLscAOYUiGQ==}
 
@@ -1618,6 +1670,11 @@ packages:
     resolution: {integrity: sha512-0pfFzegeDWJHJIAmTLRP2DwHjdF5s7jo9tuztdQxAhINCdvS+3nGINqPd00AphqJR/0LhANUS6/+7SCb98YOfA==}
     engines: {node: '>=10'}
 
+  yaml@2.6.1:
+    resolution: {integrity: sha512-7r0XPzioN/Q9kXBro/XPnA6kznR73DHq+GXh5ON7ZozRO6aMjbmiBuKste2wslTFkC5d1dw0GooOCepZXJ2SAg==}
+    engines: {node: '>= 14'}
+    hasBin: true
+
   yargs-parser@21.1.1:
     resolution: {integrity: sha512-tVpsJW7DdjecAiFpbIB1e3qxIQsE6NoPc5/eTdrbbIC4h0LVsWhnoa3g+m2HclBIujHzsxZ4VJVA+GUuc2/LBw==}
     engines: {node: '>=12'}
@@ -1946,6 +2003,12 @@ snapshots:
     dependencies:
       levn: 0.4.1
 
+  '@gerrit0/mini-shiki@1.24.4':
+    dependencies:
+      '@shikijs/engine-oniguruma': 1.24.4
+      '@shikijs/types': 1.24.4
+      '@shikijs/vscode-textmate': 9.3.1
+
   '@humanfs/core@0.19.1': {}
 
   '@humanfs/node@0.16.6':
@@ -2051,6 +2114,18 @@ snapshots:
   '@rollup/rollup-win32-x64-msvc@4.29.1':
     optional: true
 
+  '@shikijs/engine-oniguruma@1.24.4':
+    dependencies:
+      '@shikijs/types': 1.24.4
+      '@shikijs/vscode-textmate': 9.3.1
+
+  '@shikijs/types@1.24.4':
+    dependencies:
+      '@shikijs/vscode-textmate': 9.3.1
+      '@types/hast': 3.0.4
+
+  '@shikijs/vscode-textmate@9.3.1': {}
+
   '@sinclair/typebox@0.27.8': {}
 
   '@types/chai-subset@1.3.5':
@@ -2065,6 +2140,10 @@ snapshots:
 
   '@types/estree@1.0.6': {}
 
+  '@types/hast@3.0.4':
+    dependencies:
+      '@types/unist': 3.0.3
+
   '@types/istanbul-lib-coverage@2.0.6': {}
 
   '@types/json-schema@7.0.15': {}
@@ -2073,6 +2152,8 @@ snapshots:
     dependencies:
       undici-types: 6.20.0
 
+  '@types/unist@3.0.3': {}
+
   '@typescript-eslint/eslint-plugin@8.18.2(@typescript-eslint/parser@8.18.2(eslint@9.17.0(jiti@2.4.2))(typescript@5.7.2))(eslint@9.17.0(jiti@2.4.2))(typescript@5.7.2)':
     dependencies:
       '@eslint-community/regexpp': 4.12.1
@@ -2358,6 +2439,8 @@ snapshots:
 
   emoji-regex@8.0.0: {}
 
+  entities@4.5.0: {}
+
   env-paths@2.2.1: {}
 
   error-ex@1.3.2:
@@ -2680,6 +2763,10 @@ snapshots:
 
   lines-and-columns@1.2.4: {}
 
+  linkify-it@5.0.0:
+    dependencies:
+      uc.micro: 2.1.0
+
   local-pkg@0.4.3: {}
 
   locate-path@6.0.0:
@@ -2712,6 +2799,8 @@ snapshots:
     dependencies:
       get-func-name: 2.0.2
 
+  lunr@2.3.9: {}
+
   magic-string@0.30.17:
     dependencies:
       '@jridgewell/sourcemap-codec': 1.5.0
@@ -2720,6 +2809,17 @@ snapshots:
     dependencies:
       semver: 7.6.3
 
+  markdown-it@14.1.0:
+    dependencies:
+      argparse: 2.0.1
+      entities: 4.5.0
+      linkify-it: 5.0.0
+      mdurl: 2.0.0
+      punycode.js: 2.3.1
+      uc.micro: 2.1.0
+
+  mdurl@2.0.0: {}
+
   meow@12.1.1: {}
 
   merge2@1.4.1: {}
@@ -2830,6 +2930,8 @@ snapshots:
       ansi-styles: 5.2.0
       react-is: 18.3.1
 
+  punycode.js@2.3.1: {}
+
   punycode@2.3.1: {}
 
   queue-microtask@1.2.3: {}
@@ -2947,6 +3049,15 @@ snapshots:
 
   type-detect@4.1.0: {}
 
+  typedoc@0.27.6(typescript@5.7.2):
+    dependencies:
+      '@gerrit0/mini-shiki': 1.24.4
+      lunr: 2.3.9
+      markdown-it: 14.1.0
+      minimatch: 9.0.5
+      typescript: 5.7.2
+      yaml: 2.6.1
+
   typescript-eslint@8.18.2(eslint@9.17.0(jiti@2.4.2))(typescript@5.7.2):
     dependencies:
       '@typescript-eslint/eslint-plugin': 8.18.2(@typescript-eslint/parser@8.18.2(eslint@9.17.0(jiti@2.4.2))(typescript@5.7.2))(eslint@9.17.0(jiti@2.4.2))(typescript@5.7.2)
@@ -2959,6 +3070,8 @@ snapshots:
 
   typescript@5.7.2: {}
 
+  uc.micro@2.1.0: {}
+
   ufo@1.5.4: {}
 
   undici-types@6.20.0: {}
@@ -3003,7 +3116,7 @@ snapshots:
       '@types/node': 22.10.2
       fsevents: 2.3.3
 
-  vite@6.0.6(@types/node@22.10.2)(jiti@2.4.2):
+  vite@6.0.6(@types/node@22.10.2)(jiti@2.4.2)(yaml@2.6.1):
     dependencies:
       esbuild: 0.24.2
       postcss: 8.4.49
@@ -3012,6 +3125,7 @@ snapshots:
       '@types/node': 22.10.2
       fsevents: 2.3.3
       jiti: 2.4.2
+      yaml: 2.6.1
 
   vitest@0.34.6:
     dependencies:
@@ -3070,6 +3184,8 @@ snapshots:
 
   y18n@5.0.8: {}
 
+  yaml@2.6.1: {}
+
   yargs-parser@21.1.1: {}
 
   yargs@17.7.2:
diff --git a/src/camelise.ts b/src/camelise.ts
index fa29fa1..0c1fc7a 100644
--- a/src/camelise.ts
+++ b/src/camelise.ts
@@ -1,3 +1,14 @@
+/**
+ * Converts a string of words to remove spaces and capitalise each word except
+ * for the first (lowerCamelCase). If the uppercaseFirstLetter parameter is set
+ * to true, then it produces the string in UpperCamelCase, also known as
+ * PascalCase.
+ 
+ * @param words - an underscore separated string to be converted to camelcase.
+ * @param uppercaseFirstLetter - if true, the first letter will be uppercase.
+ * @returns a camelcase version of words.
+ */
+
 export default function camelise(
   words: string,
   uppercaseFirstLetter: boolean = false
diff --git a/src/dasherise.ts b/src/dasherise.ts
index 7eb8f44..dc4cae4 100644
--- a/src/dasherise.ts
+++ b/src/dasherise.ts
@@ -1,3 +1,9 @@
+/**
+ * Converts a string of words to a hyphen separated string (kebab-case).
+ *
+ * @param words - an underscore separated string to be converted to kebabcase.
+ * @returns a kebabcase version of words.
+ */
 export default function dasherise(words: string): string {
   return words.replaceAll('_', '-')
 }
diff --git a/src/downcase-first.ts b/src/downcase-first.ts
index 829563b..bf7c45f 100644
--- a/src/downcase-first.ts
+++ b/src/downcase-first.ts
@@ -1,3 +1,9 @@
+/**
+ * Converts the first word of the string to start with a lowercase character.
+ *
+ * @param words - a space separated string.
+ * @returns a copy of words that starts with a lowercase character.
+ */
 export default function downcaseFirst(words: string): string {
   return words
     .split(' ')
diff --git a/src/humanise.ts b/src/humanise.ts
index c70a805..5283453 100644
--- a/src/humanise.ts
+++ b/src/humanise.ts
@@ -1,3 +1,13 @@
+/**
+ * Converts a string of words to display better to end users by being space
+ * separated. If the uppercaseFirstLetter parameter is set to true, then the
+ * first letter of each word will also start with an uppercase letter.
+ *
+ * @param words - an underscore separated string to be made space separated.
+ * @param uppercaseFirstLetter - if true, the first letter of each word will be
+ * uppercase.
+ * @returns a space separated version of words.
+ */
 export default function humanise(
   words: string,
   uppercaseFirstLetter: boolean = false
diff --git a/src/ordinal.ts b/src/ordinal.ts
index a9c9e61..7cf6fa3 100644
--- a/src/ordinal.ts
+++ b/src/ordinal.ts
@@ -1,3 +1,10 @@
+/**
+ * Returns the suffix that can be added to a number to indicate the position in
+ * an ordered sequence, for example 1st, 42nd, or 111th.
+ *
+ * @param number - the number to determine the ordinal suffix of.
+ * @returns - the ordinal suffix that will be st, nd, rd, or th.
+ */
 export default function ordinal(number: number): string {
   switch (number % 10) {
     case 1:
diff --git a/src/ordinalise.ts b/src/ordinalise.ts
index 6a89eda..1231b66 100644
--- a/src/ordinalise.ts
+++ b/src/ordinalise.ts
@@ -1,5 +1,13 @@
 import ordinal from './ordinal'
 
+/**
+ * Converts a number into an ordinal string used to indiciate the position in an
+ * ordered sequence, for example 1st, 42nd, or 111th.
+ *
+ * @param number - the number to use as the ordinal prefix and used to determine
+ * what the ordinal suffix is.
+ * @returns the number with the correct ordinal suffix appended to it.
+ */
 export default function ordinalise(number: number): string {
   return `${number}${ordinal(number)}`
 }
diff --git a/src/parameterise.ts b/src/parameterise.ts
index 3168943..d7b272b 100644
--- a/src/parameterise.ts
+++ b/src/parameterise.ts
@@ -1,8 +1,17 @@
+/**
+ * Replaces spaces in a word with a hyphen or custom separator character so
+ * that the word may be used as part of friendly URL slug.
+ *
+ * @param word - a word to have spaces replaced by a separator.
+ * @param separator - a separator character to replace spaces with.
+ * @param preserveCase - if set to true, the word will not be made lower case.
+ * @returns a copy of the word seperated by hyphens or a custom separator.
+ */
 export default function parameterise(
   word: string,
-  seperator = '-',
+  separator = '-',
   preserveCase = false
 ): string {
   const stringToParameterise = preserveCase ? word : word.toLowerCase()
-  return stringToParameterise.split(' ').join(seperator)
+  return stringToParameterise.split(' ').join(separator)
 }
diff --git a/src/pascalise.ts b/src/pascalise.ts
index 8bf7a77..fcd248e 100644
--- a/src/pascalise.ts
+++ b/src/pascalise.ts
@@ -1,4 +1,12 @@
-export default function camelise(words: string): string {
+/**
+ * Converts a string of words to remove spaces and capitalise each word
+ * including the first (UpperCamelCase or PascalCase). To make the first word
+ * start with a lowercase character, use the camelcase function instead.
+ 
+ * @param words - an underscore separated string to be converted to pascal case.
+ * @returns a pascalcase version of words.
+ */
+export default function pascalise(words: string): string {
   return words
     .split('_')
     .map((word) => {
diff --git a/src/titleise.ts b/src/titleise.ts
index 510b816..90cc20b 100644
--- a/src/titleise.ts
+++ b/src/titleise.ts
@@ -1,5 +1,11 @@
 import { letterIsUpperCase } from './shared-functions'
 
+/**
+ * Capitalises each word in the specified string.
+ *
+ * @param words - a string of words to be titleised.
+ * @returns a copy of words where each word starts with an uppercase character.
+ */
 export default function titleise(words: string): string {
   return words
     .trim()
diff --git a/src/underscore.ts b/src/underscore.ts
index 2c80ee8..f84661a 100644
--- a/src/underscore.ts
+++ b/src/underscore.ts
@@ -1,5 +1,11 @@
 import { letterIsUpperCase } from './shared-functions'
 
+/**
+ * Converts a camelcase separated string of words to be underscore separated.
+ *
+ * @param words - a camelcase separated string of words.
+ * @returns a copy of words where each word is underscore separated.
+ */
 export default function underscore(words: string): string {
   return words
     .split('')
diff --git a/src/upcase-first.ts b/src/upcase-first.ts
index 0626cd7..46e7689 100644
--- a/src/upcase-first.ts
+++ b/src/upcase-first.ts
@@ -1,3 +1,9 @@
+/**
+ * Converts the first word of the string to start with an uppercase character.
+ *
+ * @param words - a space separated string.
+ * @returns a copy of words that starts with an uppercase character.
+ */
 export default function upcaseFirst(words: string): string {
   return words
     .split(' ')