ext-apps/examples/cohort-heatmap-server/README.md
Jonathan Hefner 4ca20f21c4
Smoothen the process of getting started (#103)
* Restructure threejs-server README to match marketing examples

- Update title format to "Example: Three.js App"
- Constrain screenshot width using table layout
- Add Features section with key capabilities
- Reorganize Running section with Tool Input subsection
- Add Architecture section describing server and app components
- Remove implementation-focused sections (WidgetProps, Creating a New Widget)

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* Add bun as devDependency to example packages

npm install now automatically installs bun, eliminating the need for
separate installation instructions. Removed manual bun install step
from customer-segmentation-server README.

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* Add start:http and start:stdio npm scripts to examples

For the 6 examples supporting --stdio transport, add explicit scripts:
- serve:http / serve:stdio for running the server
- start:http / start:stdio for build + serve
- start now aliases to start:http for backward compatibility

Update READMEs to document both transport options.

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* Default basic-host SERVERS to localhost:3001/mcp

- Change threejs-server default port from 3109 to 3001 for consistency
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- Document SERVERS env var in basic-host README

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* Improve Examples section in README

Frame the three basic examples as foundational starting points and
add a link to the examples directory for additional demo apps.

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Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
2025-12-09 16:15:32 +01:00

2.6 KiB

Example: Cohort Heatmap App

A demo MCP App that displays cohort retention data as an interactive heatmap, showing customer retention over time by signup month.

Initial view Hover state Low retention hover

Features

  • Cohort Retention Heatmap: Color-coded grid showing retention percentages across cohorts and time periods
  • Multiple Metrics: Switch between Retention %, Revenue Retention, and Active Users
  • Period Types: View data by monthly or weekly intervals
  • Interactive Exploration: Hover cells for detailed tooltips, click to highlight rows/columns
  • Color Scale: Green (high retention) through yellow to red (low retention)
  • Theme Support: Adapts to light/dark mode preferences

Running

  1. Install dependencies:

    npm install
    
  2. Build and start the server:

    npm run start:http  # for Streamable HTTP transport
    # OR
    npm run start:stdio  # for stdio transport
    
  3. View using the basic-host example or another MCP Apps-compatible host.

Architecture

Server (server.ts)

Exposes a single get-cohort-data tool that returns:

  • Cohort rows with signup month, original user count, and retention cells
  • Period headers and labels
  • Configurable parameters: metric type, period type, cohort count, max periods

The tool generates synthetic cohort data using an exponential decay model with configurable retention curves per metric type.

App (src/mcp-app.tsx)

  • Uses React for the heatmap visualization
  • Fetches data on mount and when filters change
  • Displays retention percentages in a grid with HSL color interpolation
  • Shows detailed tooltips on hover with user counts and exact retention values
  • Supports row/column highlighting on cell click