Skip to content

docs(skill): add CSP location and CORS pitfalls to common mistakes #407

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
antonpk1 wants to merge 2 commits into
base: main
Choose a base branch
from
+15 −0
Open

docs(skill): add CSP location and CORS pitfalls to common mistakes #407

Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
e4d92c2
docs(skill): add CSP location and CORS pitfalls to common mistakes
antonpk1 Jan 30, 2026
5aa4c6c
docs(skill): simplify CSP example
antonpk1 Jan 30, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
15 changes: 15 additions & 0 deletions plugins/mcp-apps/skills/create-mcp-app/SKILL.md
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -312,6 +312,21 @@ See `examples/shadertoy-server/` for complete implementation.
6. **No text fallback** - Always provide `content` array for non-UI hosts
7. **Hardcoded styles** - Use host CSS variables for theme integration
8. **No streaming for large inputs** - Use `ontoolinputpartial` to show progress during generation
9. **CSP `_meta` in wrong location** - Put `_meta.ui.csp` in the `contents` array (readCallback), NOT in the `registerResource` config. Only the contents location is read by hosts:
```typescript
async () => ({
contents: [{
uri, mimeType, text: html,
_meta: { ui: { csp: { connectDomains: ["https://api.example.com"] } } }
}]
})
```
10. **Localhost in CSP blocked** - CSP validation blocks `localhost`, `127.0.0.1`, and private IPs to prevent security issues. Use a tunnel (Cloudflare, ngrok) for local development.
11. **CORS vs CSP confusion** - CSP controls what *your app can request*. CORS controls what *external servers will accept*. If requests fail with "No Access-Control-Allow-Origin header", that's a CORS issue on the target server, not CSP. Use `ui.domain` to get a stable origin for CORS allowlists:
```bash
# Compute your stable origin for CORS allowlist
node -e "console.log(require('crypto').createHash('sha256').update('https://your-server.com/mcp').digest('hex').slice(0,32)+'.claudemcpcontent.com')"
```

## Testing

Expand Down
Loading