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 magnus919/agent-skills --skill backend-engineeringgit clone --depth 1 https://github.com/magnus919/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/magnus919/agent-skills/backend-engineering)<a href="https://agentmods.dev/skills/magnus919/agent-skills/backend-engineering"><img src="https://agentmods.dev/badge/skills/magnus919/agent-skills/backend-engineering/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/magnus919/agent-skills/backend-engineering"><img src="https://agentmods.dev/badge/skills/magnus919/agent-skills/backend-engineering.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector pass
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 | $0.00091 | $0.02013 |
| Opus 5.5 | $0.00036 | $0.00805 |
| Sonnet 5.5 | $0.00018 | $0.00403 |
| Haiku 4.5 | $0.00009 | $0.00201 |
Grade A, and why
backend-engineering 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 — 109 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Backend Engineering Methodology
Backend engineering is the craft of building the server-side systems that power applications — APIs, services, data access, integrations, and the runtime behavior that makes the architecture real. This methodology covers implementation after target design in software-architecture and before quality validation in qa-methodology; use software-architecture-analysis when the current system must first be reverse-engineered. It makes runtime boundaries, transaction behavior, message handling, and coexistence seams executable without taking ownership of the surrounding architecture or migration decision.
The Backend Engineer's Domain
| You own | You don't own |
|---|---|
| API implementation — REST/gRPC/GraphQL endpoints, request validation, response formatting, error handling, middleware chains | API contracts belong to api-design-and-evolution; service decomposition and target boundaries belong to software-architecture |
| Service logic — business rules, workflow orchestration, state management, background job processing | Deployment pipeline and infrastructure — that's platform-engineering |
| Event-driven implementation — domain-event publication, outbox/inbox coordination, handler idempotency, replay and failure paths | Event contract ownership and delivery semantics — that's the api-design-and-evolution |
| Migration seams inside a service — adapters, selectable paths, authority checks, and implementation handoffs | Cross-system migration lifecycle and cutover authority — that's the migration-engineering |
| Database access patterns — query design, connection management, transaction boundaries, N+1 detection, pagination | Data-platform and model strategy belong to data-architect; schema and pipeline operations belong to data-engineering |
| Integration code — third-party API clients, webhook handlers, message queue consumers/producers | Code review and quality gates — that's qa-methodology |
| Observability instrumentation at the service level — structured logging, metrics, tracing hooks | Observability infrastructure and reliability policy belong to platform-engineering and site-reliability-engineering |
| Service-level tests — unit tests for business logic, integration tests for API contracts | Test strategy and automation — that's qa-methodology |
What ships with it
14 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.
- evals/evals.json 17 KB
- README.md 2.4 KB
- references/api-patterns.md 2.2 KB
- references/database-testing.md 42 KB
- references/error-handling.md 1.9 KB
- references/event-driven-service-implementation.md 7.6 KB
- references/integration-patterns.md 1.9 KB
- references/migration-coexistence-patterns.md 5.8 KB
- references/service-patterns.md 3.3 KB
- references/source-index.md 1.9 KB
- scripts/n1-query-spotter.py 9.1 KB runs code
- scripts/test_n1_query_spotter.py 7.5 KB runs code
- templates/error-handling-taxonomy.md 3.0 KB
- templates/service-design-record.md 4.3 KB
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 · 109 lines · 91 tokens per session scan A d081df543319
backend-engineering is a skill published in the GitHub repository magnus919/agent-skills (147 stars, last pushed yesterday), licensed MIT. It adds 91 tokens to every session and 2,013 once invoked, about $0.0004 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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