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 itseffi/agentic-os --skill backend-designgit clone --depth 1 https://github.com/itseffi/agentic-osWrote 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/itseffi/agentic-os/backend-design)<a href="https://agentmods.dev/skills/itseffi/agentic-os/backend-design"><img src="https://agentmods.dev/badge/skills/itseffi/agentic-os/backend-design/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/itseffi/agentic-os/backend-design"><img src="https://agentmods.dev/badge/skills/itseffi/agentic-os/backend-design.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 | $0.00025 | $0.00404 |
| Opus 5.5 | $0.00010 | $0.00162 |
| Sonnet 5.5 | $0.00005 | $0.00081 |
| Haiku 4.5 | $0.00003 | $0.00040 |
Grade A, and why
backend-design 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.
What it actually says
Backend Design
Use this skill to design robust backend changes before implementation.
The Process
Step 1: Define backend objective
Clarify:
- business objective
- service boundary
- latency/reliability expectations
Step 2: Define API and contract changes
Specify:
- endpoints/events
- request/response schemas
- error model and status mapping
Step 3: Define data model and migrations
Document:
- schema changes
- migration strategy
- backward-compatibility approach
Step 4: Define security and observability
Include:
- authn/authz requirements
- rate limiting/abuse controls
- logging, metrics, tracing
- alerting conditions
Step 5: Define rollout and verification
Provide:
- phased rollout or feature flags
- rollback strategy
- verification checks and commands
Output Format
# [Feature Name] Backend Design Spec
## Objective
- Goal:
- Service boundary:
## API Contracts
- Endpoint/event definitions:
- Request/response schema:
- Error model:
## Data Model
- Schema changes:
- Migration plan:
- Compatibility notes:
## Security and Reliability
- Authn/authz:
- Abuse controls:
- Reliability constraints:
## Observability
- Logs:
- Metrics:
- Traces:
- Alerts:
## Rollout and Verification
- Rollout plan:
- Rollback plan:
- Verification commands/evidence:
Quality Bar
- Contracts must be explicit and testable
- Migration and rollback must be present for schema changes
- Verification must include observable evidence
When to Use
Use this skill when the task directly matches the workflow described above.
When Not to Use
Do not use this skill when the request is unrelated, low-stakes, or better handled by a simpler direct response.
What ships with it
1 file 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 · 97 lines · 25 tokens per session scan A be1b64453b50
backend-design is a skill published in the GitHub repository itseffi/agentic-os (117 stars, last pushed 14d ago), licensed MIT. It adds 25 tokens to every session and 404 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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