domain

domain is an agent for coding agents from svyatov/handrail. It costs 0 tokens per session (397 once invoked), scanned A, a copy of domain, MIT.

A guide for using a repository’s domain documentation while exploring and changing its code. Domain documentation explains the project’s business terms, boundaries, and recorded architecture decisions.

In plain words
What is it for?
Reading the root context file and relevant architecture decision records before exploring code, naming concepts, writing issues, or proposing refactors.
Why use it?
It helps coding work use the project’s established vocabulary and decisions instead of making assumptions or introducing conflicting terms.

Agent

Part of the handrail plugin — 2 skills, 4 agents, 1 hook 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 agents/svyatov/handrail/domain
Clone the repo
git clone --depth 1 https://github.com/svyatov/handrail

Or install handrail, the plugin that ships this one along with the rest of its 2 skills, 4 agents, 1 hook.

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 domain

README.md
[![agentmods](https://agentmods.dev/badge/agents/svyatov/handrail/domain.svg)](https://agentmods.dev/agents/svyatov/handrail/domain)
Your own site
<a href="https://agentmods.dev/agents/svyatov/handrail/domain"><img src="https://agentmods.dev/badge/agents/svyatov/handrail/domain.svg" alt="Measured on agentmods" height="20"></a>
Per session 0 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 397 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin 80% copy Near-identical to another mod 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 $0.00000 $0.00397
Opus 5 $0.00000 $0.00198
Sonnet 5 $0.00000 $0.00079
Haiku 4.5 $0.00000 $0.00040

Measured 3d ago against content hash f58341105c1d, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

domain 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 3d 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.

Origin

This is a copy

80% identical to domain — 34 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

docs/agents/domain.md · 38 lines

What it actually says

Domain docs

How the engineering skills should consume this repo's domain documentation when exploring the codebase.

This repo is single-context: one CONTEXT.md and one docs/adr/ at the root.

Before exploring, read these

  • CONTEXT.md at the repo root
  • docs/adr/: read ADRs that touch the area you're about to work in.

If any of these files don't exist, proceed silently. Don't flag their absence; don't suggest creating them upfront. The /domain-modeling skill (reached via /grill-with-docs and /improve-codebase-architecture) creates them lazily when terms or decisions actually get resolved.

File structure

/
├── CONTEXT.md
├── docs/adr/
│   ├── 0001-example-decision.md
│   └── 0002-another-decision.md
└── src/

If this repo ever splits into multiple bounded contexts, add a root CONTEXT-MAP.md pointing at one CONTEXT.md per context, with context-scoped src/<context>/docs/adr/ directories, and update this file.

Use the glossary's vocabulary

When your output names a domain concept (in an issue title, a refactor proposal, a hypothesis, a test name), use the term as defined in CONTEXT.md. Don't drift to synonyms the glossary explicitly avoids.

If the concept you need isn't in the glossary yet, that's a signal: either you're inventing language the project doesn't use (reconsider) or there's a real gap (note it for /domain-modeling).

Flag ADR conflicts

If your output contradicts an existing ADR, surface it explicitly rather than silently overriding:

Contradicts ADR-0007 (event-sourced orders), but worth reopening because…

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. 3d ago First seen · 38 lines · 0 tokens per session scan A f58341105c1d

Subscribe to this mod's changes

domain is an agent published in the GitHub repository svyatov/handrail (2 stars, last pushed 10d ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 397 tokens. A static security scan graded it A with 0 findings. It is 80% identical to domain, differing in 34 lines, and is treated as a copy.

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