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What it does

Ask Claude Code (or any MCP client):

Design the home dashboard for a fitness tracker. Three concentric activity rings, weekly bar chart, recent workouts list, premium dark mode with neon accents.

mockit-mcp returns a real PNG mockup (sized 390×844 at 2x device scale, an iPhone-class viewport) and the underlying HTML/Tailwind source — so you can iterate visually and port to SwiftUI when you're ready to build.

It's not a static template engine and it's not generic AI slop. The system prompt is hand-tuned for premium iOS aesthetics: real content, SVG icons (no emoji), tasteful gradients in place of stock photos, iOS HIG type scale, and tonal layering instead of heavy shadows.

Related MCP server: Playwright MCP for macOS

Highlights

  • Two backends, same tools. Use the local claude CLI (subscription, $0 extra) or the Anthropic API (key + per-call pricing). Switch with one env var.

  • Real PNG output. Headless Chromium via Playwright. Default viewport is 390×844 @2x (iPhone-class); any custom size is one env var away.

  • Iterative refinement. iterate_screen takes a screen ID + feedback ("make the hero card smaller") and produces a new version, tracking parent/child.

  • Disk-backed library. Every generation saves HTML + PNG + JSON metadata. Browse, filter, re-export.

  • MCP standard. Works with Claude Code, Claude Desktop, Cursor, Windsurf, or any MCP client.

  • Stdio + HTTP transports. Run locally for dev, or as a network service for shared / containerized use.

Tools

Tool

Description

generate_screen

Text brief → PNG + HTML. Optional design_system and project fields.

iterate_screen

Take a previous screen_id + feedback string, produce a new version.

list_screens

List screens, optionally filtered by project.

get_screen

Fetch metadata (or full HTML) for a specific screen.

Install

Prerequisites

  • Node.js 20+

  • Either the claude CLI logged in (cli backend, default) or an Anthropic API key (api backend)

  • Playwright's Chromium download (~170 MB, one-time)

git clone https://github.com/karyaboyraz/mockit-mcp.git
cd mockit-mcp
npm install
npx playwright install chromium
npm run build

Add to Claude Code:

claude mcp add mockit -- node "$(pwd)/dist/server.js"

Done. No API key needed — it uses your existing claude CLI session.

API backend (no claude CLI on host)

echo "CLAUDE_BACKEND=api" > .env
echo "ANTHROPIC_API_KEY=sk-ant-..." >> .env
npm run build
claude mcp add mockit -- node "$(pwd)/dist/server.js"

Docker (HTTP transport, for shared deployment)

cat > .env <<'ENV'
CLAUDE_BACKEND=api
ANTHROPIC_API_KEY=sk-ant-...
# Required if you change the port binding from 127.0.0.1 to 0.0.0.0:
MCP_HTTP_TOKEN=$(openssl rand -hex 32)
ENV
docker compose up -d --build

By default docker-compose.yml binds the HTTP port to 127.0.0.1 only and the server requires MCP_HTTP_TOKEN for any non-loopback request. Don't expose this server to a public network without setting a strong MCP_HTTP_TOKEN — every generation hits your Anthropic API key.

Then point any client at the loopback URL:

claude mcp add --transport http mockit http://127.0.0.1:7821/mcp \
  -H "Authorization: Bearer <MCP_HTTP_TOKEN>"

For remote access, change docker-compose.yml's port binding to 0.0.0.0:7821:7821 and ensure MCP_HTTP_TOKEN is set — the server refuses to start otherwise.

Usage

In any MCP client, just ask:

Design a fitness tracker dashboard. Show today's ring progress, a weekly chart, and a list of recent workouts. Dark mode, neon green accent.

The PNG appears inline. The HTML is saved to designs/{project}/{name}-{id}.html.

For follow-ups:

iterate_screen on that fitness dashboard — replace the chart with heart-rate over time, and add a "share workout" button below.

See examples/ for prompt patterns and full outputs.

Configuration

All optional. See .env.example for the full list.

Env

Default

Notes

CLAUDE_BACKEND

cli

cli uses the claude CLI; api uses Anthropic SDK directly

ANTHROPIC_API_KEY

Required only for api backend

ANTHROPIC_MODEL

claude-opus-4-7

API backend only. If your account doesn't have Opus access, set to claude-sonnet-4-6 or claude-haiku-4-5

CLAUDE_CLI_PATH

claude

Path to the claude binary

CLAUDE_CLI_TIMEOUT_MS

180000

Subprocess timeout

MCP_TRANSPORT

stdio

stdio or http

HTTP_PORT

7821

HTTP transport port

HTTP_HOST

127.0.0.1

Bind interface; non-loopback requires MCP_HTTP_TOKEN

MCP_HTTP_TOKEN

Bearer token for HTTP auth. Required if HTTP_HOST is non-loopback

DESIGNS_DIR

./designs

Where outputs are persisted

VIEWPORT_WIDTH

390

Render width in CSS pixels

VIEWPORT_HEIGHT

844

Render height in CSS pixels

DEVICE_SCALE

2

Retina factor (final PNG is WIDTH × DEVICE_SCALE wide)

PLAYWRIGHT_NO_SANDBOX

auto

auto = sandbox enabled outside containers; true to force-disable, false to force-enable. Disabling reduces isolation against malicious model HTML — only do so inside a container.

Cost

Per generation: ~3K input tokens (system prompt) + ~6–12K output tokens depending on screen complexity. Output dominates the cost on Opus.

Backend

First call

Cached follow-up

cli

counts against your Claude Code subscription quota

same — cache only discounts the system prompt

api

~$0.50–0.95 (Opus 4.7)

~$0.45–0.90 (cache discounts the system-prompt input only; output cost is unchanged)

System-prompt caching is on by default (5-minute TTL). It saves a few cents per call but is not an order-of-magnitude discount — output tokens still bill at full rate. For real cost reduction, switch to a smaller model (claude-sonnet-4-6 or claude-haiku-4-5).

Architecture

┌─────────────────┐
│   MCP Client    │  (Claude Code, Cursor, Windsurf, …)
└────────┬────────┘
         │ tool call: generate_screen({ prompt, ... })
         ▼
┌─────────────────────────────────────────────────────┐
│  mockit-mcp                                          │
│                                                      │
│  ┌──────────────┐    ┌────────────────────────┐    │
│  │  Backend     │    │  Renderer              │    │
│  │              │    │                        │    │
│  │ ► cli   ─────┼──► │  Playwright (headless  │    │
│  │ ► api   ─────┘    │  Chromium @ iPhone     │    │
│  │  → HTML+Tailwind  │  viewport)             │    │
│  └──────────────┘    │  → PNG screenshot      │    │
│                      └────────────────────────┘    │
│                                                      │
│  ┌────────────────────────────────────────────┐    │
│  │ Storage (disk): HTML + PNG + JSON metadata │    │
│  └────────────────────────────────────────────┘    │
└─────────────────────────────────────────────────────┘

Storage layout

designs/
└── {project-slug}/
    ├── {name-slug}-{id8}.html   # id8 = first 8 chars of the screen UUID
    ├── {name-slug}-{id8}.png
    └── {name-slug}-{id8}.json   # full UUID, prompt, parent ID, tokens, model, cost

Documentation

Reference and guides live in docs/:

Topic

Page

Install, first generation, verify

Getting Started

Every env var, defaults, what they do

Configuration

The four MCP tools — schemas, examples

Tools Reference

Pipeline end-to-end

Architecture

Local, Docker, networked deployments

Deployment

Sandbox, network allowlist, HTTP auth

Security

How the design voice is encoded

System Prompt

Common errors and how to fix them

Troubleshooting

Tuning the design voice

The hand-tuned system prompt lives in src/system-prompt.ts. It's where the iOS HIG enforcement, the no-stock-photo rule, the SF Pro fallback chain, and the editorial typography preferences are encoded. Want Material You instead, or a desktop dashboard voice? Edit it.

Development

npm run dev    # tsx watch mode, stdio transport
npm run http   # tsx watch mode, http transport on :7821
npm run build  # compile to dist/

Roadmap

  • Watch / iPad / Android viewport presets

  • Multi-screen flow generation (onboarding sequences)

  • HTML → SwiftUI / Jetpack Compose port tool

  • Design system import (Tailwind config, design tokens)

  • Image references (use --image for visual inspiration)

  • Variant generation (3-5 alternatives per prompt)

Contributing

Issues and PRs welcome — see CONTRIBUTING.md.

License

MIT

Acknowledgements

Built on top of:

Trademarks

iPhone, iPad, Apple Watch, and iOS are trademarks of Apple Inc. Claude is a trademark of Anthropic, PBC. mockit-mcp is an independent open-source project and is not affiliated with, endorsed by, or sponsored by Apple Inc. or Anthropic, PBC. All other product names, logos, and brands are property of their respective owners.

Available Tools

4 tools
generate_screenA

Generate a premium iOS mobile UI mockup from a text brief. Outputs both the screenshot (PNG) and the underlying HTML. Use this when the user asks to design, mock up, or visualize a mobile app screen.

ParametersJSON Schema
NameRequiredDescriptionDefault
promptYesDetailed brief for the screen: what app, what screen, what content, what UI elements.
projectNoProject name (used to group related screens).default
nameYesShort name for this screen, e.g. 'Main', 'Settings', 'Onboarding'.
design_systemNoOptional design system spec: colors, fonts, voice. If omitted, the system invents one consistent with the prompt.

TDQS

A4/5.0
Behavior3/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

No annotations are provided, so the description carries the full burden. It discloses that the tool outputs both a screenshot (PNG) and HTML, which is a key behavioral trait. However, it does not cover other aspects like potential costs, authentication needs, rate limits, or side effects. This is moderate transparency.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is two sentences long, front-loaded with the core functionality in the first sentence and usage guidance in the second. Every word earns its place; no fluff or redundancy.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the tool has 4 parameters, no output schema, and no annotations, the description provides sufficient context for basic usage: what it generates and when to use it. It could be improved by mentioning the response format or error handling, but for a generation tool with clear output, it is fairly complete.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The input schema has 100% description coverage for its 4 parameters. The description adds minimal extra meaning beyond the schema, except for the context of 'premium iOS mobile UI mockup' which gives design direction. Baseline 3 is appropriate as schema does heavy lifting.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the tool generates a premium iOS mobile UI mockup from a text brief, with both screenshot and HTML output. It distinguishes itself from siblings (get_screen, iterate_screen, list_screens) by focusing on creation rather than retrieval or iteration.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description explicitly says 'Use this when the user asks to design, mock up, or visualize a mobile app screen.' This provides clear context for when to use, though it does not explicitly list when not to use or mention alternatives. However, the context of sibling tools implies those alternatives.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

get_screenA

Get details and metadata for a specific screen. Set include_html=true to also return the HTML source.

ParametersJSON Schema
NameRequiredDescriptionDefault
screen_idYesScreen UUID returned by generate_screen or iterate_screen.
include_htmlNoInclude full HTML in response (large).

TDQS

A3.7/5.0
Behavior3/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations, the description carries the burden. It mentions the optional HTML return but does not disclose potential size impacts, pagination, or any side effects. Minimal but not misleading.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Two concise sentences that directly state the tool's purpose and key parameter option. No wasted words.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness3/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

No output schema, so 'details and metadata' is vague. While the tool is simple, an agent might benefit from knowing what fields are returned. Adequate but not fully complete.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, and the description adds minimal extra meaning beyond what the schema already states. For screen_id, it repeats the schema; for include_html, it rephrases slightly.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states it 'get details and metadata for a specific screen,' which distinguishes it from siblings like generate_screen (create) and list_screens (list all).

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines3/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

No explicit guidance on when to use this versus alternatives, though sibling names imply the correct use case. The description does provide context for an optional parameter (include_html).

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

iterate_screenA

Refine an existing generated screen based on feedback. Use this for follow-up edits like 'change color', 'add a section', 'make it more spacious'.

ParametersJSON Schema
NameRequiredDescriptionDefault
screen_idYesID of the screen to iterate on (from generate_screen output).
feedbackYesWhat to change: 'make the hero card larger', 'use orange accent instead of blue', etc.
nameNoOptional new name for the iteration. Defaults to original name + ' (v2)'.

TDQS

A4/5.0
Behavior3/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations, the description carries full burden for behavioral disclosure. It implies mutation ("refine") but does not specify whether changes are reversible, what permissions are needed, or how the tool handles multiple iterations. The examples are non-destructive, but explicit security or side-effect info is missing.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is two sentences, front-loaded with the primary action, and includes practical examples without extraneous text. Every sentence adds value and the structure is efficient.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given no output schema and no annotations, the description adequately explains the tool's purpose and gives usage examples. However, it does not describe the return value (e.g., updated screen object) or confirm that screen_id must come from generate_screen, which is noted only in the schema. A bit more context on how to use the result would improve completeness.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Input schema has 100% coverage, so baseline is 3. The description adds minimal extra meaning beyond the schema's parameter descriptions (e.g., "feedback" examples). The optional "name" parameter is described in both, but the description reinforces but does not significantly augment the schema.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the tool refines an existing generated screen based on feedback, distinguishing it from siblings like generate_screen (creation) and get_screen (retrieval). The examples of feedback ("change color", "add a section") further clarify its purpose.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description specifies that this tool is for follow-up edits after generation, providing clear usage context. However, it does not explicitly state when not to use it (e.g., for new screens or non-generated screens) or mention prerequisites like valid screen_id from generate_screen.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

list_screensA

List all generated screens, optionally filtered by project name.

ParametersJSON Schema
NameRequiredDescriptionDefault
projectNoFilter by project. Omit to list all.

TDQS

A4.2/5.0
Behavior4/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

The description implies a read-only operation without side effects, which is transparent for a list tool. No annotations exist, but the description is clear.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is a single, concise sentence that efficiently conveys the tool's purpose and optional parameter without extraneous information.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a simple list tool with one optional parameter and no output schema, the description is adequate. It could be more complete by mentioning the return format, but it still provides sufficient context for an AI agent.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100% with a clear description of the 'project' parameter. The tool description adds 'optionally filtered by project name' but does not add significant new meaning beyond the schema.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the action ('list') and resource ('generated screens') with an optional filter. It distinguishes from siblings like generate_screen and get_screen.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description implies when to use (listing all screens) and mentions optional filtering, but does not explicitly state when not to use or compare to alternatives like iterate_screen.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

Tool Schema Changelog

Recent tool additions, removals, and schema changes observed during successful MCP inspections. Dates show when Glama detected each change.

  1. 4 tool updatesv0.1.1
    • First observedgenerate_screen
    • First observedget_screen
    • First observediterate_screen
    • First observedlist_screens

TDQS

A4.2/5.0
Disambiguation5/5

Each tool serves a distinct purpose: generate creates, get retrieves, iterate refines, list enumerates. No functional overlap.

Naming Consistency5/5

All tools follow a consistent verb_noun pattern in snake_case (generate_screen, get_screen, iterate_screen, list_screens).

Tool Count5/5

4 tools is well-scoped for a mockup generation service, covering creation, retrieval, iteration, and listing without excess.

Completeness4/5

Covers core CRUD except delete, which may be intentional. Users can create, read, update, and list screens, with no obvious dead ends.

Maintenance

ActivityInactive
ResponsivenessNo issues

Resources

Unclaimed servers have limited discoverability.

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