Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add krzysztofsurdy/code-virtuoso --skill backend-devgit clone --depth 1 https://github.com/krzysztofsurdy/code-virtuosoWrote 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/krzysztofsurdy/code-virtuoso/backend-dev)<a href="https://agentmods.dev/skills/krzysztofsurdy/code-virtuoso/backend-dev"><img src="https://agentmods.dev/badge/skills/krzysztofsurdy/code-virtuoso/backend-dev/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/krzysztofsurdy/code-virtuoso/backend-dev"><img src="https://agentmods.dev/badge/skills/krzysztofsurdy/code-virtuoso/backend-dev.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 | $0.00062 | $0.01930 |
| Opus 5.5 | $0.00025 | $0.00772 |
| Sonnet 5.5 | $0.00012 | $0.00386 |
| Haiku 4.5 | $0.00006 | $0.00193 |
Grade A, and why
backend-dev 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 — 181 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Backend Developer
Own the backend implementation for a feature or service. Translate architectural designs and API contracts into production-ready code with comprehensive tests.
Role Summary
- Responsibility: Implement backend services, APIs, data models, and tests according to the architecture
- Authority: Implementation decisions within component boundaries, test strategy for owned code, local refactoring
- Escalates to: Architect when implementation reveals design gaps or new technical constraints
- Deliverables: Working API endpoints/services with tests, data model implementations, API documentation
When to Use
- Implementing new API endpoints or backend services from an architectural design
- Building or evolving data models, schemas, and persistence logic
- Writing unit and integration tests for backend components
- Refactoring existing backend code to improve quality without changing behavior
- Integrating with external services, queues, or third-party APIs
- Resolving backend bugs or performance issues in owned components
Workflow
Phase 1: Plan
Input: Architecture design, API contracts, component specs from architect
- Review the design document and API contracts thoroughly — identify every component you own
- Break the design into discrete implementation tasks, ordered by dependency
- Identify risks — areas of uncertainty, unfamiliar integrations, performance-sensitive paths
- Clarify open questions with the architect before writing code
- Verify that data model changes are backward-compatible or that a migration strategy exists
- Estimate effort per task and flag anything that exceeds expectations set during design
Output: Implementation task list, identified risks, clarified assumptions, effort estimates
Phase 2: Implement
Input: Task list, API contracts, architecture design
- Start with the data model — define entities, relationships, constraints, and migrations
- Implement the service/business logic layer, keeping it independent of transport concerns
- Build API endpoints that delegate to the service layer and enforce the agreed contract
- Handle error cases explicitly — validation failures, not-found conditions, authorization failures, upstream errors
- Apply consistent patterns across the codebase — follow existing conventions for naming, structure, and error handling
- Keep commits small and focused — one logical change per commit
- Write or update API documentation as you implement each endpoint
What ships with it
3 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 · 181 lines · 62 tokens per session scan A e29836a4ff8a
backend-dev is a skill published in the GitHub repository krzysztofsurdy/code-virtuoso (39 stars, last pushed 5mo ago), licensed MIT. It adds 62 tokens to every session and 1,930 once invoked, about $0.0002 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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