# System Context Builder

> >

- **Type:** Skill
- **Install:** `agentstack add skill-patonkikh-apes-system-context-builder`
- **Verified:** Yes — security-reviewed for prompt injection and unsafe behavior
- **Seller:** [patonkikh](https://agentstack.voostack.com/s/patonkikh)
- **Installs:** 0
- **Category:** [AI & ML](https://agentstack.voostack.com/c/ai-and-ml)
- **Latest version:** 0.1.0
- **License:** MIT
- **Upstream author:** [patonkikh](https://github.com/patonkikh)
- **Source:** https://github.com/patonkikh/APES/tree/main/skills/architecture/system-context-builder

## Install

```sh
agentstack add skill-patonkikh-apes-system-context-builder
```

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

## About

# System Context Builder

# Purpose

Produce a C4 Level 1 (System Context) diagram and description showing the system, its users, and external dependencies.

**Input:** Solution architecture or PRD, stakeholder list (optional)  
**Output:** System Context document with Mermaid diagram, actor descriptions, and external system inventory
**Examples:** See [examples.md](examples.md) for worked input/output.

---

# Workflow

## Step 1: Identify the system boundary

Define:

- System name and one-sentence purpose
- What is inside the system boundary
- What is explicitly outside

## Step 2: Identify actors (users and personas)

List all human actors:

| Actor | Type (user/admin/operator) | Goal | Interaction |
|-------|------------------------------|------|-------------|

Map to personas from product skills if available.

## Step 3: Identify external systems

List all external systems the solution interacts with:

| System | Purpose | Protocol | Data exchanged | Owned by |
|--------|---------|----------|----------------|----------|

Include: identity providers, payment, email, analytics, third-party APIs.

## Step 4: Draw context diagram

Use Mermaid C4-style or flowchart:

```mermaid
flowchart LR
    actor1[Actor] --> system[System]
    system --> ext1[External System]
```

Rules:

- One central system node
- Actors on the left/top
- External systems on the right/bottom
- Label every arrow with action or data flow

## Step 5: Document trust boundaries

Identify security boundaries between system and externals.

## Step 6: Validate

Run Validation checklist.

---

# Decision Rules

| Condition | Action |
|-----------|--------|
| No solution architecture or PRD | Stop; request input or run solution-architecture |
| Actor overlaps with external system | Clarify: human actor vs software system |
| More than 10 external systems | Group into categories; detail in appendix |
| Undocumented integration | Mark as "TBD"; add to open questions |
| System boundary unclear | Ask user to confirm scope before diagramming |

---

# Validation

- [ ] System boundary explicitly defined
- [ ] All actors from PRD/user flows represented
- [ ] All external integrations listed
- [ ] Mermaid diagram renders with labeled relationships
- [ ] Trust boundaries identified
- [ ] No container-level detail (defer to container-diagram-builder)
- [ ] Diagram matches written descriptions

---

# Anti-patterns

- **Missing externals** — ignoring auth provider, payment, email services.
- **Container in context** — showing databases or internal services at Level 1.
- **Unlabeled arrows** — relationships without action/data description.
- **Actor = system** — treating batch jobs or admin tools as users without clarity.
- **Scope creep** — including future-phase systems without marking as planned.

---

# Best Practices

- Follow C4 Model Level 1 strictly.
- Use consistent naming from solution architecture components at abstract level.
- Mark planned vs current integrations.
- Align actors with PRD user flows.
- Keep diagram readable: max 7±2 nodes.

---

# Output Structure

```markdown
# System Context: [System Name]

## System
**Name:** [name]
**Purpose:** [one sentence]
**Boundary:** [what's in/out]

## Actors
| Actor | Type | Goal | Interactions |
|-------|------|------|--------------|

## External Systems
| System | Purpose | Protocol | Data | Status |
|--------|---------|----------|------|--------|

## Context Diagram
```mermaid
[diagram]
```

## Trust Boundaries
| Boundary | Controls |
|----------|----------|

## Open Questions
- [ ] [Question]
```

---

# Next Skills

| Outcome | Recommended Skill |
|---------|-------------------|
| Decompose into containers | `architecture/container-diagram-builder` |
| Design APIs for externals | `architecture/api-designer` |
| Update solution architecture | `architecture/solution-architecture` |
| Record integration decisions | `architecture/adr-generator` |

## Source & license

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

- **Author:** [patonkikh](https://github.com/patonkikh)
- **Source:** [patonkikh/APES](https://github.com/patonkikh/APES)
- **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-patonkikh-apes-system-context-builder
- Seller: https://agentstack.voostack.com/s/patonkikh
- 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%.