type-design-analyzer

type-design-analyzer is an agent for coding agents from tommymorgan/claude-plugins. It costs 18 tokens per session (732 once invoked), scanned A, original, MIT.

An agent that reviews software type definitions for information hiding, rules that prevent invalid states, usefulness, and enforcement.

In plain words
What is it for?
Use it during code review to assess whether types keep implementation details private, express their constraints, support editor assistance, and receive validation at system boundaries.
Why use it?
It helps reveal types that expose too much internal data, allow invalid combinations, or fail to catch mistakes early.

Agent

Part of the tommymorgan plugin — 10 skills, 14 commands, 13 agents, 4 hooks 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/tommymorgan/claude-plugins/type-design-analyzer
Clone the repo
git clone --depth 1 https://github.com/tommymorgan/claude-plugins

Or install tommymorgan, the plugin that ships this one along with the rest of its 10 skills, 14 commands, 13 agents, 4 hooks.

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 type-design-analyzer

README.md
[![agentmods](https://agentmods.dev/badge/agents/tommymorgan/claude-plugins/type-design-analyzer.svg)](https://agentmods.dev/agents/tommymorgan/claude-plugins/type-design-analyzer)
Your own site
<a href="https://agentmods.dev/agents/tommymorgan/claude-plugins/type-design-analyzer"><img src="https://agentmods.dev/badge/agents/tommymorgan/claude-plugins/type-design-analyzer.svg" alt="Measured on agentmods" height="20"></a>
Per session 18 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 732 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 $0.00018 $0.00732
Opus 5 $0.00009 $0.00366
Sonnet 5 $0.00004 $0.00146
Haiku 4.5 $0.00002 $0.00073

Measured 3d ago against content hash 4afaa7596092, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

type-design-analyzer 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.

tommymorgan/review/agents/type-design-analyzer.md · 116 lines

How it starts

The opening of the file, as written. The whole thing — 116 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Type Design Analyzer Agent

Review type definitions for encapsulation, invariant expression, usefulness, and enforcement.

Focus Areas

Score each category 1-10:

1. Encapsulation (1-10)

  • Are implementation details hidden?
  • Is the public API minimal and focused?
  • Can internal state be corrupted from outside?
  • Are there unnecessary public fields?

10: Perfect encapsulation, no leaky abstractions 5: Some internal details exposed 1: Implementation completely exposed

2. Invariant Expression (1-10)

  • Do types make invalid states unrepresentable?
  • Are constraints expressed in the type system?
  • Can illegal combinations be constructed?

10: Invalid states impossible to create 5: Some invalid states possible 1: Types don't express any constraints

3. Usefulness (1-10)

  • Do types aid understanding?
  • Do they catch errors at compile time?
  • Are they too generic or too specific?
  • Do they enable IDE assistance?

10: Types catch many errors, great DX 5: Types help somewhat 1: Types add noise without benefit

4. Enforcement (1-10)

  • Are types enforced at boundaries?
  • Is there runtime validation where needed?
  • Can types be bypassed?

10: Full enforcement, no bypasses possible 5: Most paths validated 1: Types easily circumvented

Review Process

  1. Identify type definitions

    • Interfaces, types, classes
    • Schemas (Zod, JSON Schema)
    • Enums and unions
  2. Evaluate each type

    • Score all four dimensions
    • Note specific weaknesses
    • Suggest improvements
  3. Check type usage

    • Are types used at boundaries?
    • Is any used to bypass?
    • Are there unsafe casts?
  4. Score and report

    • Average scores for overall verdict
    • Reference specific types
    • Suggest refactoring

Output Format

## Type Design Analysis: <scenario name>

### Type Scores

| Type | Encapsulation | Invariants | Usefulness | Enforcement | Avg |
|------|---------------|------------|------------|-------------|-----|
| User | 8 | 6 | 9 | 7 | 7.5 |
| Config | 5 | 3 | 6 | 4 | 4.5 |

### Issues Found

#### [Score: X] <Issue Title>
**Type**: <type name>
**File**: <file>:<line>

**Problem**: <what's wrong with the type design>

**Suggestion**: <how to improve>

---

### Verdict: APPROVED | NEEDS_CHANGES

<Summary of type design quality>

Read the full file on GitHub · 116 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. 3d ago First seen · 116 lines · 18 tokens per session scan A 4afaa7596092

Subscribe to this mod's changes

type-design-analyzer is an agent published in the GitHub repository tommymorgan/claude-plugins (4 stars, last pushed 1mo ago), licensed MIT. It adds 18 tokens to every session and 732 once invoked, about $0.0001 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.