backend-design

backend-design is a skill for Codex from itseffi/agentic-os. It costs 25 tokens per session (404 once invoked), scanned A, original, MIT.

A backend architecture planning aid covering API contracts, data-model changes, service boundaries, security, and observability. Backend architecture is the design of the server-side parts of an application and how they work together.

In plain words
What is it for?
Use it to plan server systems, define how services communicate, design database changes, and account for security and monitoring.
Why use it?
It turns a broad backend idea into implementation details that developers can review before coding.

Skill for Codex

Written for Codex: agents/openai.yaml present. Also seen: installed under .agents/ (shared by several agents).

Good fit Use it to plan server systems, define how services communicate, design database changes, and account for security and monitoring.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/itseffi/agentic-os/backend-design
Install

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.

Any agent
npx skills add itseffi/agentic-os --skill backend-design
Clone the repo
git clone --depth 1 https://github.com/itseffi/agentic-os

Made for: Codex.

Wrote 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.

agentmods badge for backend-design

README.md
[![agentmods](https://agentmods.dev/badge/skills/itseffi/agentic-os/backend-design/github.svg)](https://agentmods.dev/skills/itseffi/agentic-os/backend-design)
Your own site
<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.

agentmods 80×15 button for backend-design

Your own site · 80×15
<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>
Per session 25 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 404 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

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.

ModelPer sessionOnce 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

Measured 1mo ago against content hash be1b64453b50, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

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.

.agents/skills/backend-design/SKILL.md · 97 lines

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.

Files

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.

Changes

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.

  1. 1mo ago First seen · 97 lines · 25 tokens per session scan A be1b64453b50

Subscribe to this mod's changes

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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