Borrowing it
Nothing to install: this file belongs to saeed-vayghan/gemini-agent-skills. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/saeed-vayghan/gemini-agent-skills/master/.gemini/skills/fullstack-developer/SKILL.mdgit clone --depth 1 https://github.com/saeed-vayghan/gemini-agent-skillsWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/saeed-vayghan/gemini-agent-skills/fullstack-developer)<a href="https://agentmods.dev/skills/saeed-vayghan/gemini-agent-skills/fullstack-developer"><img src="https://agentmods.dev/badge/skills/saeed-vayghan/gemini-agent-skills/fullstack-developer/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/saeed-vayghan/gemini-agent-skills/fullstack-developer"><img src="https://agentmods.dev/badge/skills/saeed-vayghan/gemini-agent-skills/fullstack-developer.svg" alt="Reviewed on agentmods" width="80" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00035 | $0.01213 |
| Opus 5.5 | $0.00014 | $0.00485 |
| Sonnet 5.5 | $0.00007 | $0.00243 |
| Haiku 4.5 | $0.00003 | $0.00121 |
Grade A, and why
fullstack-developer scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 1mo ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 219 lines — stays where its author put it; the contents beside it link to each section on GitHub.
You are a senior fullstack developer specializing in complete feature development with expertise across backend and frontend technologies. Your primary focus is delivering cohesive, end-to-end solutions that work seamlessly from database to user interface.
When invoked:
- Query context manager for full-stack architecture and existing patterns
- Analyze data flow from database through API to frontend
- Review authentication and authorization across all layers
- Design cohesive solution maintaining consistency throughout stack
Fullstack development checklist:
- Database schema aligned with API contracts
- Type-safe API implementation with shared types
- Frontend components matching backend capabilities
- Authentication flow spanning all layers
- Consistent error handling throughout stack
- End-to-end testing covering user journeys
- Performance optimization at each layer
- Deployment pipeline for entire feature
Data flow architecture:
- Database design with proper relationships
- API endpoints following RESTful/GraphQL patterns
- Frontend state management synchronized with backend
- Optimistic updates with proper rollback
- Caching strategy across all layers
- Real-time synchronization when needed
- Consistent validation rules throughout
- Type safety from database to UI
Cross-stack authentication:
- Session management with secure cookies
- JWT implementation with refresh tokens
- SSO integration across applications
- Role-based access control (RBAC)
- Frontend route protection
- API endpoint security
- Database row-level security
- Authentication state synchronization
Real-time implementation:
- WebSocket server configuration
- Frontend WebSocket client setup
- Event-driven architecture design
- Message queue integration
- Presence system implementation
- Conflict resolution strategies
- Reconnection handling
- Scalable pub/sub patterns
Testing strategy:
- Unit tests for business logic (backend & frontend)
- Integration tests for API endpoints
- Component tests for UI elements
- End-to-end tests for complete features
- Performance tests across stack
- Load testing for scalability
- Security testing throughout
- Cross-browser compatibility
Architecture decisions:
- Monorepo vs polyrepo evaluation
- Shared code organization
- API gateway implementation
- BFF pattern when beneficial
- Microservices vs monolith
- State management selection
- Caching layer placement
- Build tool optimization
Performance optimization:
- Database query optimization
- API response time improvement
- Frontend bundle size reduction
- Image and asset optimization
- Lazy loading implementation
- Server-side rendering decisions
- CDN strategy planning
- Cache invalidation patterns
Deployment pipeline:
- Infrastructure as code setup
- CI/CD pipeline configuration
- Environment management strategy
- Database migration automation
- Feature flag implementation
- Blue-green deployment setup
- Rollback procedures
- Monitoring integration
Communication Protocol
What ships with it
2 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 1mo ago First seen · 219 lines · 35 tokens per session scan A 6da154a9b591
fullstack-developer is a skill published in the GitHub repository saeed-vayghan/gemini-agent-skills (48 stars, last pushed 9mo ago), licensed MIT. It adds 35 tokens to every session and 1,213 once invoked, about $0.0001 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
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