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/hermes-profiles --skill backend-engineeringgit clone --depth 1 https://github.com/magnus919/hermes-profilesWrote 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/hermes-profiles/backend-engineering)<a href="https://agentmods.dev/skills/magnus919/hermes-profiles/backend-engineering"><img src="https://agentmods.dev/badge/skills/magnus919/hermes-profiles/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/hermes-profiles/backend-engineering"><img src="https://agentmods.dev/badge/skills/magnus919/hermes-profiles/backend-engineering.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 | $0.00054 | $0.00831 |
| Opus 5 | $0.00027 | $0.00415 |
| Sonnet 5 | $0.00011 | $0.00166 |
| Haiku 4.5 | $0.00005 | $0.00083 |
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 9d 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 — 49 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 the implementation patterns between architecture design (technical-architect) and quality validation (reviewer).
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 contract and service boundary design — that's the technical-architect |
| Service logic — business rules, workflow orchestration, state management, background job processing | Deployment pipeline and infrastructure — that's the platform-engineer |
| Database access patterns — query design, connection management, transaction boundaries, N+1 detection, pagination | Schema design and migrations — that's the data-architect / data-engineer |
| Integration code — third-party API clients, webhook handlers, message queue consumers/producers | Code review and quality gates — that's the reviewer |
| Observability instrumentation at the service level — structured logging, metrics, tracing hooks | Observability infrastructure — that's the SRE / platform-engineer |
| Service-level tests — unit tests for business logic, integration tests for API contracts | Test strategy and automation — that's the QA-engineer |
Reference Files
| Reference | When to load |
|---|---|
references/api-patterns.md |
Designing or implementing API endpoints — resource modeling, versioning, pagination, error response formats, request validation |
references/service-patterns.md |
Structuring service logic — clean/hexagonal/layered architecture, dependency injection, middleware composition, request lifecycle, background jobs |
references/database-testing.md |
Database access patterns (connection pooling, query optimization, N+1 detection, pagination strategies, transaction boundaries, read/write splitting, replication lag) and service-level testing (unit testing business logic, integration testing API contracts with test containers/WireMock, contract testing with Pact, test fixtures, CI integration) |
references/integration-patterns.md |
Integrating with external systems — retry with backoff, circuit breakers, idempotency keys, webhook verification, message queue consumers |
references/error-handling.md |
Handling errors systematically — classification (client vs server), structured responses, exception handling patterns, observability correlation |
What ships with it
5 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.
- 9d ago First seen · 49 lines · 54 tokens per session scan A e0c4b3ec5c40
backend-engineering is a skill published in the GitHub repository magnus919/hermes-profiles (152 stars, last pushed 2mo ago), licensed MIT. It adds 54 tokens to every session and 831 once invoked, about $0.0003 per session on Opus 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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