chore: add usage skill for AI agents

Adds a SKILL.md file in .agents/skills/usage/ following the Agent Skills
spec for cross-client compatibility with Claude, Cursor, and OpenClaw.

Made-with: Cursor

Author: Cursor

.agents/skills/usage/SKILL.md

@@ -0,0 +1,121 @@
+---
+name: python-proxy-headers-usage
+description: >-
+  Send and receive custom headers during HTTPS CONNECT tunneling in Python.
+  Use when integrating proxy headers with requests, httpx, aiohttp, urllib3,
+  pycurl, cloudscraper, or autoscraper.
+---
+
+# python-proxy-headers
+
+Send custom headers to proxies and receive proxy response headers during HTTPS CONNECT tunneling.
+
+## Installation
+
+```bash
+pip install python-proxy-headers
+```
+
+Install your HTTP client as needed (requests, httpx, aiohttp, etc.).
+
+## Quick Reference
+
+| Library | Module | Main Class/Function |
+|---------|--------|---------------------|
+| requests | `python_proxy_headers.requests_adapter` | `ProxySession` |
+| httpx | `python_proxy_headers.httpx_proxy` | `get`, `post`, etc. |
+| aiohttp | `python_proxy_headers.aiohttp_proxy` | `ProxyClientSession` |
+| urllib3 | `python_proxy_headers.urllib3_proxy_manager` | `ProxyHeadersPoolManager` |
+| pycurl | `python_proxy_headers.pycurl_proxy` | `set_proxy_headers`, `HeaderCapture` |
+| cloudscraper | `python_proxy_headers.cloudscraper_proxy` | `create_scraper` |
+| autoscraper | `python_proxy_headers.autoscraper_proxy` | `ProxyAutoScraper` |
+
+## Usage Patterns
+
+### requests
+
+```python
+from python_proxy_headers.requests_adapter import ProxySession
+
+with ProxySession(proxy_headers={'X-ProxyMesh-Country': 'US'}) as session:
+    session.proxies = {'https': 'http://user:pass@proxy.example.com:8080'}
+    response = session.get('https://httpbin.org/ip')
+    print(response.headers.get('X-ProxyMesh-IP'))
+```
+
+### httpx
+
+```python
+from python_proxy_headers.httpx_proxy import get
+
+response = get(
+    'https://httpbin.org/ip',
+    proxy='http://user:pass@proxy.example.com:8080'
+)
+print(response.headers.get('X-ProxyMesh-IP'))
+```
+
+### aiohttp
+
+```python
+import asyncio
+from python_proxy_headers.aiohttp_proxy import ProxyClientSession
+
+async def main():
+    async with ProxyClientSession() as session:
+        async with session.get(
+            'https://httpbin.org/ip',
+            proxy='http://user:pass@proxy.example.com:8080'
+        ) as response:
+            print(response.headers.get('X-ProxyMesh-IP'))
+
+asyncio.run(main())
+```
+
+### pycurl
+
+```python
+import pycurl
+from python_proxy_headers.pycurl_proxy import set_proxy_headers, HeaderCapture
+
+c = pycurl.Curl()
+c.setopt(pycurl.URL, 'https://httpbin.org/ip')
+c.setopt(pycurl.PROXY, 'http://proxy.example.com:8080')
+
+set_proxy_headers(c, {'X-ProxyMesh-Country': 'US'})
+capture = HeaderCapture(c)
+
+c.perform()
+print(capture.proxy_headers)
+c.close()
+```
+
+### cloudscraper
+
+```python
+from python_proxy_headers.cloudscraper_proxy import create_scraper
+
+scraper = create_scraper(proxy_headers={'X-ProxyMesh-Country': 'US'})
+scraper.proxies = {'https': 'http://proxy.example.com:8080'}
+response = scraper.get('https://example.com')
+```
+
+## Common Headers
+
+| Header | Direction | Purpose |
+|--------|-----------|---------|
+| `X-ProxyMesh-Country` | Send | Route through specific country |
+| `X-ProxyMesh-IP` | Send/Receive | Request or receive sticky IP |
+
+## Testing
+
+```bash
+export PROXY_URL='http://user:pass@proxy.example.com:8080'
+python test_proxy_headers.py -v
+# or specific modules:
+python test_proxy_headers.py requests httpx
+```
+
+## Documentation
+
+Full docs at [python-proxy-headers.readthedocs.io](https://python-proxy-headers.readthedocs.io/).