# Check First

> |

- **Type:** Skill
- **Install:** `agentstack add skill-bearded-illirian-trailmark-check-first`
- **Verified:** Yes — security-reviewed for prompt injection and unsafe behavior
- **Seller:** [bearded-illirian](https://agentstack.voostack.com/s/bearded-illirian)
- **Installs:** 0
- **Category:** [AI & ML](https://agentstack.voostack.com/c/ai-and-ml)
- **Latest version:** 0.1.0
- **License:** MIT
- **Upstream author:** [bearded-illirian](https://github.com/bearded-illirian)
- **Source:** https://github.com/bearded-illirian/trailmark/tree/main/aihub/.claude/skills/check-first

## Install

```sh
agentstack add skill-bearded-illirian-trailmark-check-first
```

Requires the [AgentStack CLI](https://agentstack.voostack.com/docs/cli). Works with Claude Code, Cursor, and any MCP-compatible agent.

## About

# Check-First Protocol

Runs after a decomposition step in any workflow (e.g. after proposing
epics for a brief, or blocks for a specification). Verifies that every
requirement from the source document is covered by at least one
proposed unit.

---

## Step 1 — Extract requirements

From the already-read requirements document (brief, specification,
technical description, product doc) extract every requirement. Look in
sections like:

- Scope / What's included
- Acceptance criteria
- What must exist
- Functional requirements
- Non-functional requirements

Each requirement is one row. Don't duplicate near-identical items —
merge them if the essence is the same.

---

## Step 2 — Output a coverage table

```
Requirements coverage check:

┌─────┬────────────────────────────────────┬──────────────┬────────────┐
│  #  │ Requirement                        │ Unit         │ Status     │
├─────┼────────────────────────────────────┼──────────────┼────────────┤
│ 1   │ [requirement from source doc]      │ Unit N       │ ✅ Covered │
│ 2   │ [requirement from source doc]      │ Unit N       │ ✅ Covered │
│ 3   │ [requirement from source doc]      │ —            │ ⚠️ Gap     │
└─────┴────────────────────────────────────┴──────────────┴────────────┘
```

"Unit" = the smallest labelled thing in your decomposition: an epic, a
block, a task — whatever the current workflow produces.

---

## Step 3 — Decision

**If every row is ✅:**

```
✅ All requirements covered — continuing.
```

Proceed without pause.

**If there are ⚠️ gaps:**

```
⚠️ N gap(s) found. Options:
1. Add to an existing unit [Unit X]
2. Create a new unit
3. Move to backlog — not part of this cycle
```

Wait for user decision per gap. After decisions land — update the unit
list and continue.

---

## Rules

- Don't skip even when the decomposition looks obviously complete
- On gaps — don't proceed without a user decision
- Extract requirements from the source text, don't invent them
- The point of the protocol is a paper trail: even a "no gaps" result
  is a first-class artifact — future readers see what was checked

---

## Anti-patterns

### ❌ Skipping when decomposition looks obvious

The decomposition seems to fully cover the requirements — skip the
check. Later a requirement surfaces in production, and nobody can
reconstruct whether it was considered or missed.

**Rule:** always run coverage check, even for "obvious" decomposition.
Even a "no gaps" result is a first-class artifact.

### ❌ Inventing requirements

The agent invents a requirement to make unit N fit — user approves.
The actual source document never contained that requirement, and the
decomposition now includes phantom work.

**Rule:** extract from source text only. If a unit doesn't map to any
extracted requirement, that's a signal the unit itself is scope creep,
not that a requirement is "implicit".

### ❌ Silent gap dismissal

Agent finds a gap → decides «it's minor, skip» → doesn't surface to
user. Later the gap becomes a bug or missed feature, and there's no
record of the decision to skip.

**Rule:** every gap requires an explicit user decision (add / new unit
/ backlog). Never dismiss silently. Recording "we chose to defer this"
is itself the audit trail.

### ❌ Inlining instead of Skill()

The agent read the protocol from memory and executed it inline — no
coverage-table artifact, no logged decision, no paper trail.

**Rule:** always launch via `Skill('check-first')` tool. The whole
value of the protocol is the artifact it produces.

---

## Related skills

- **plan-first** — invokes check-first after outputting the plan
  decomposition table, before executing
- **arch-first** — decomposition source for larger multi-block tasks;
  check-first validates coverage against the original brief/spec
- **ship-first** — closes work; check-first ensures nothing missed
  before the block or task is marked done

---

## Step 99 — Log invocation

Before exiting, log this skill invocation to routing.db:

```bash
sqlite3 {routing_db} \
  "INSERT INTO skill_invocations (task_id, block_num, skill_name, invoked_at)
   VALUES ('{slug}', '{N}', 'check-first', datetime('now'))" 2>/dev/null || true
```

If `{slug}` / `{N}` unknown → hook writes empty; `|| true` guards failure.

## Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

- **Author:** [bearded-illirian](https://github.com/bearded-illirian)
- **Source:** [bearded-illirian/trailmark](https://github.com/bearded-illirian/trailmark)
- **License:** MIT

Install and usage instructions live in the source repository linked above.

## Pricing

- **Free** — Free

## Security capabilities

Automated source analysis of v0.1.0 — what this tool can access:

- **Network access:** no
- **Filesystem access:** no
- **Shell / process execution:** no
- **Environment & secrets:** no
- **Dynamic code execution:** no

*"Yes" means the capability is present in the source — more access means more to trust, not that it is unsafe.*


## Versions

- **0.1.0** — security scan: passed — Imported from the upstream source.

## Links

- Listing page: https://agentstack.voostack.com/l/skill-bearded-illirian-trailmark-check-first
- Seller: https://agentstack.voostack.com/s/bearded-illirian
- Browse the marketplace: https://agentstack.voostack.com/browse

---
Listed on AgentStack — the marketplace for AI agent skills and MCP servers. Every listing is security-reviewed. Creators keep 70%.