backend-mvp-guardrails

backend-mvp-guardrails is a skill for Claude Code, Codex from victorGPT/vibeusage. It costs 43 tokens per session (1,152 once invoked), scanned A, original, MIT.

A set of rules for building a small backend that uses changing data and outside services. It focuses on repeatable writes, rebuildable summaries, limited queries, and evidence for identifying failures.

In plain words
What is it for?
Use it when designing or reviewing a budget-constrained backend MVP. It helps plan data storage, retries, schema changes, query limits, and incident investigation.
Why use it?
It reduces the risk of duplicate records, lost data, expensive database work, and confusion about whether your code or an outside provider caused an incident.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

Good fit Use it when designing or reviewing a budget-constrained backend MVP. It helps plan data storage, retries, schema changes, query limits, and incident investigation.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/victorgpt/vibeusage/backend-mvp-guardrails
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 victorGPT/vibeusage --skill backend-mvp-guardrails
Clone the repo
git clone --depth 1 https://github.com/victorGPT/vibeusage

Made for: Claude Code, 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-mvp-guardrails

README.md
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Your own site
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agentmods 80×15 button for backend-mvp-guardrails

Your own site · 80×15
<a href="https://agentmods.dev/skills/victorgpt/vibeusage/backend-mvp-guardrails"><img src="https://agentmods.dev/badge/skills/victorgpt/vibeusage/backend-mvp-guardrails.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 43 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,152 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. A grade says what 26 rules found in the file — not that it is safe. Third-party audits
  • NVIDIA SkillSpector pass 7 Sept 2026
How audits are shown
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 $0.00043 $0.01152
Opus 5 $0.00022 $0.00576
Sonnet 5 $0.00009 $0.00230
Haiku 4.5 $0.00004 $0.00115

Measured 10d ago against content hash 728685ebfb10, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-10, from the pricing page.

Security

Grade A, and why

backend-mvp-guardrails scanned grade A with 1 finding 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 10d 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.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

const res = await fetch(upstreamUrl);
docs/skills/backend-mvp-guardrails/SKILL.md · 128 lines

How it starts

The opening of the file, as written. The whole thing — 128 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Backend MVP Guardrails

Overview

Minimize irreversible decisions. Every write must be idempotent, every aggregate must be replayable, and every incident must be attributable with minimal evidence.

When to Use

  • MVP backend with single-digit USD/month budget or strict capacity limits
  • Fast schema evolution or new data sources with unknown fields
  • Third-party backend dependency (e.g., InsForge) with no status page or DB metrics
  • Repeated ambiguity about whether failures are vendor or application issues

When NOT to use: throwaway prototypes where data loss and misattribution are acceptable.

Core Pattern (Two Layers)

Layer 1: Principle Guardrails (platform-agnostic)

  1. Source of truth is immutable or append-only. Avoid online recomputation on read paths.
  2. Idempotent writes. Deterministic keys + upsert or unique constraint.
  3. Replayable aggregates. Derived tables can be rebuilt from the source of truth.
  4. Evidence-first attribution. No structured evidence, no blame, no destructive fix.
  5. Cost-first queries. Pre-aggregate, cap ranges, enforce limits, avoid full scans.
  6. Schema evolution is additive. New fields are optional and versioned; unknown fields are rejected by allowlist.

Layer 2: Platform Mapping (InsForge example)

  • Fact table: half-hour buckets (e.g., vibescore_tracker_hourly)
  • Idempotency key: user_id + device_id + source + model + hour_start
  • Aggregates: derived from buckets; do not read raw event tables for dashboards
  • Retention: keep aggregates longer; cap any event-level tables
  • Backfill: limited window + upsert; must be replayable
  • Observability: M1 structured logs (see below)

Responsibility Attribution Protocol (M1)

Required fields: request_id, function, stage, status, latency_ms, error_code, upstream_status, upstream_latency_ms

Attribution rules:

  • Missing upstream_status => UNKNOWN (do not change data semantics)
  • upstream_status is 5xx/timeout and function status is 5xx => likely vendor/backbone issue
  • upstream_status is 2xx and function status is 4xx/5xx => likely application validation/logic issue
  • latency_ms high and upstream_latency_ms low => likely application-side bottleneck

Read the full file on GitHub · 128 lines

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. 10d ago First seen · 128 lines · 43 tokens per session scan A 728685ebfb10

Subscribe to this mod's changes

backend-mvp-guardrails is a skill published in the GitHub repository victorGPT/vibeusage (131 stars, last pushed 1mo ago), licensed MIT. It adds 43 tokens to every session and 1,152 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 1 finding (makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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