diff --git a/README.md b/README.md
index 5be3af1..9662caa 100644
--- a/README.md
+++ b/README.md
@@ -254,13 +254,19 @@ When using nxapi as a TypeScript/JavaScript library, the `addUserAgent` function
 import { addUserAgent } from 'nxapi';
 
 addUserAgent('your-script/1.0.0 (+https://github.com/...)');
+```
 
-// This could also be read from a package.json file
-import { fileURLToPath } from 'node:url';
-import { resolve } from 'node:path';
-import { readFile } from 'node:fs/promises':
-const pkg = JSON.parse(await readFile(resolve(fileURLToPath(import.meta.url), '..', 'package.json'), 'utf-8'));
-addUserAgent(pkg.name + '/' + pkg.version + ' (+' + pkg.repository.url + ')');
+The `addUserAgentFromPackageJson` function can be used to add data from a package.json file.
+
+```ts
+import { addUserAgentFromPackageJson } from 'nxapi';
+
+await addUserAgentFromPackageJson(new URL('../package.json', import.meta.url));
+await addUserAgentFromPackageJson(path.resolve(fileURLToString(import.meta.url), '..', 'package.json'));
+// adds "test-package/0.1.0 (+https://github.com/ghost/example.git)"
+
+await addUserAgentFromPackageJson(new URL('../package.json', import.meta.url), 'additional information');
+// adds "test-package/0.1.0 (+https://github.com/ghost/example.git; additional information)"
 ```
 
 ### Usage as a TypeScript/JavaScript library
diff --git a/docs/lib/index.md b/docs/lib/index.md
index 9cc174a..6f32f8d 100644
--- a/docs/lib/index.md
+++ b/docs/lib/index.md
@@ -151,6 +151,10 @@ try {
 
 This function is used to set the user agent string to use for non-Nintendo API requests. Any project using nxapi (including as a dependency of another project) must call this function with an appropriate user agent string segment. See [user agent strings](../../README.md#user-agent-strings).
 
+#### `addUserAgentFromPackageJson`
+
+This function is used to set the user agent string to use for non-Nintendo API requests using data from a package.json file. A string, URL object or the package.json data can be provided, as well as optional additional data. If a string/URL is provided this will return a Promise that will be resolved once the user agent is updated. See [user agent strings](../../README.md#user-agent-strings).
+
 #### `version`
 
 nxapi's version number.
diff --git a/src/exports/index.ts b/src/exports/index.ts
index 6e120fd..011f8fe 100644
--- a/src/exports/index.ts
+++ b/src/exports/index.ts
@@ -1,6 +1,6 @@
 export { getTitleIdFromEcUrl } from '../util/misc.js';
 export { ErrorResponse, ResponseSymbol } from '../api/util.js';
-export { addUserAgent } from '../util/useragent.js';
+export { addUserAgent, addUserAgentFromPackageJson } from '../util/useragent.js';
 
 export { version } from '../util/product.js';
 
diff --git a/src/util/useragent.ts b/src/util/useragent.ts
index 4cea42d..f65d7b0 100644
--- a/src/util/useragent.ts
+++ b/src/util/useragent.ts
@@ -1,5 +1,6 @@
 import * as process from 'node:process';
 import * as os from 'node:os';
+import * as fs from 'node:fs/promises';
 import { docker, git, release, version } from '../util/product.js';
 
 const default_useragent = 'nxapi/' + version + ' (' +
@@ -19,6 +20,68 @@ export function addUserAgent(...useragent: string[]) {
     additional_useragents.push(...useragent);
 }
 
+export function addUserAgentFromPackageJson(pkg: string | URL, additional?: string): Promise<void>;
+export function addUserAgentFromPackageJson(pkg: object, additional?: string): void;
+export function addUserAgentFromPackageJson(pkg: string | URL | object, additional?: string) {
+    if (typeof pkg === 'string' || pkg instanceof URL) {
+        return fs.readFile(pkg, 'utf-8').then(pkg => addUserAgentFromPackageJson(JSON.parse(pkg)));
+    }
+
+    const name = 'name' in pkg && typeof pkg.name === 'string' ? pkg.name : null;
+    const version = 'version' in pkg && typeof pkg.version === 'string' ? pkg.version : null;
+    if (!name || !version) throw new Error('package.json does not contain valid name and version fields');
+
+    const homepage = 'homepage' in pkg ? pkg.homepage : null;
+    if (homepage != null && typeof homepage !== 'string') throw new Error('package.json contains an invalid homepage field');
+    const repository = 'repository' in pkg && pkg.repository != null ?
+        getPackageJsonRepository(pkg.repository) : null;
+
+    const end =
+        (homepage ? '+' + homepage : repository ? '+' + repository.url : '') +
+        (repository && additional ? '; ' : '') +
+        additional;
+
+    const useragent = name + '/' + version + (end ? ' (' + end + ')' : '');
+
+    addUserAgent(useragent);
+}
+
+function getPackageJsonRepository(repository: unknown): {
+    type: string; url: string; directory?: string | null;
+} {
+    if (typeof repository === 'string') {
+        if (repository.startsWith('github:')) {
+            return {type: 'git', url: 'https://github.com/' + repository.substr(7)};
+        }
+        if (repository.startsWith('gist:')) {
+            return {type: 'git', url: 'https://gist.github.com/' + repository.substr(5)};
+        }
+        if (repository.startsWith('bitbucket:')) {
+            return {type: 'git', url: 'https://bitbucket.org/' + repository.substr(10)};
+        }
+        if (repository.startsWith('gitlab:')) {
+            return {type: 'git', url: 'https://gitlab.com/' + repository.substr(7)};
+        }
+        if (repository.match(/^[0-9a-z-.]+\/[0-9a-z-.]+$/i)) {
+            return {type: 'git', url: 'https://github.com/' + repository};
+        }
+    }
+
+    if (typeof repository === 'object' && repository) {
+        if ('type' in repository && typeof repository.type === 'string' &&
+            'url' in repository && typeof repository.url === 'string' &&
+            (!('directory' in repository) || repository.directory == null || typeof repository.directory === 'string')
+        ) {
+            return {
+                type: repository.type, url: repository.url,
+                directory: 'directory' in repository ? repository.directory as string : null,
+            };
+        }
+    }
+
+    throw new Error('package.json contains an invalid repository field');
+}
+
 /**
  * Only used by cli/nso/http-server.ts.
  * This command is intended to be run automatically and doesn't make any requests itself, so this function removes