adr-fundamentals

adr-fundamentals is a skill for Claude Code from zircote-plugins/adr. It costs 68 tokens per session (1,511 once invoked), scanned A, original, MIT.

A guide to Architectural Decision Records, short documents that record important software-architecture choices, their context, and their consequences.

In plain words
What is it for?
Use it when choosing technologies, system patterns, APIs, data storage, security methods, or other changes affecting multiple parts of a system.
Why use it?
It helps teams remember why a decision was made and makes difficult trade-offs visible to people who join later. It also explains when a decision is significant enough to document.

Skill for Claude Code

Written for Claude Code: shipped in a Claude Code plugin.

Part of the adr plugin — 12 skills, 7 commands, 3 agents shipped together

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.

agentmods
npx agentmods add skills/zircote-plugins/adr/adr-fundamentals
Any agent
npx skills add zircote-plugins/adr --skill adr-fundamentals
Clone the repo
git clone --depth 1 https://github.com/zircote-plugins/adr

Made for: Claude Code.

Or install adr, the plugin that ships this one along with the rest of its 12 skills, 7 commands, 3 agents.

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 adr-fundamentals

README.md
[![agentmods](https://agentmods.dev/badge/skills/zircote-plugins/adr/adr-fundamentals.svg)](https://agentmods.dev/skills/zircote-plugins/adr/adr-fundamentals)
Your own site
<a href="https://agentmods.dev/skills/zircote-plugins/adr/adr-fundamentals"><img src="https://agentmods.dev/badge/skills/zircote-plugins/adr/adr-fundamentals.svg" alt="Measured on agentmods" height="20"></a>
Per session 68 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,511 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
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 $0.00068 $0.01511
Opus 5 $0.00034 $0.00756
Sonnet 5 $0.00014 $0.00302
Haiku 4.5 $0.00007 $0.00151

Measured 6d ago against content hash 3f7a8ea771bd, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-06, from the pricing page.

Security

Grade A, and why

adr-fundamentals 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 6d 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.

skills/adr-fundamentals/SKILL.md · 221 lines

How it starts

The opening of the file, as written. The whole thing — 221 lines — stays where its author put it; the contents beside it link to each section on GitHub.

ADR Fundamentals

Architectural Decision Records (ADRs) capture important architectural decisions along with their context and consequences. This skill provides foundational knowledge for creating, managing, and maintaining ADRs effectively.

When to Create an ADR

Create an ADR when making decisions that:

  • Have significant impact - Affect system structure, behavior, or quality attributes
  • Are hard to reverse - Would require substantial effort to change later
  • Have multiple viable options - Alternatives were seriously considered
  • Affect multiple components - Cross-cutting concerns or system-wide patterns
  • Set precedent - Establish patterns others will follow
  • Involve trade-offs - Balance competing concerns or constraints

Common ADR-Worthy Decisions

Category Examples
Technology Selection Programming language, framework, database, cloud provider
Architecture Patterns Microservices vs monolith, event-driven, CQRS
API Design REST vs GraphQL, versioning strategy, authentication
Data Management Storage strategy, caching, replication, backup
Security Authentication method, encryption, access control
Integration Third-party services, messaging patterns, protocols
Infrastructure Container orchestration, deployment strategy, scaling

When NOT to Create an ADR

Skip ADRs for:

  • Routine implementation choices
  • Decisions with obvious answers
  • Temporary or experimental changes
  • Minor configuration tweaks
  • Decisions that can be easily reversed

ADR Lifecycle

Status Workflow

proposed → accepted → [deprecated] → superseded
              ↓
          rejected
Status Meaning
proposed Under consideration, open for discussion
accepted Approved and active, guides current development
rejected Considered but not adopted (document why)
deprecated No longer recommended, pending replacement
superseded Replaced by a newer ADR (link to successor)

Read the full file on GitHub · 221 lines

Files

What ships with it

4 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.

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. 6d ago First seen · 221 lines · 68 tokens per session scan A 3f7a8ea771bd

Subscribe to this mod's changes

adr-fundamentals is a skill published in the GitHub repository zircote-plugins/adr (5 stars, last pushed 19d ago), licensed MIT. It adds 68 tokens to every session and 1,511 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 2026-08-31.

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