MCP App Test Value Picker Server

You can run a focused test MCP server that verifies end-to-end communication between an MCP Apps host and the AI model. This value picker server provides a simple UI test where a user selects a value, and the platform must propagate that selection through ui/update-model-context and respond to follow-up messages via ui/message. It helps you validate context injection, message forwarding, and the complete View → Host → Model flow.

How to use

Connect this MCP server to your MCP Apps host. Run the server in the mode that matches your environment, then deploy your host to exercise the pick_value tool. When the UI presents 10 values, selecting one should trigger ui/update-model-context with the chosen value’s details and then a follow-up ui/message asking for the AI to identify the selected value. Your platform passes the selected value to the AI, and the AI should respond with the correct value as a confirmation.

How to install

Prerequisites: you need Node.js and npm or npx available on your machine.

Install the MCP App Test Value Picker server globally using npm, which provides the mcp-server-value-picker CLI.

Run the server in automatic transport-detection mode by executing the CLI with no extra arguments.

If you prefer to force a specific transport, you can run the CLI with --stdio for STDIO mode or --http for HTTP mode.

Alternatively, you can run the server without installation by using npx.

How to install (concrete steps)

# Install globally (recommended)
npm install -g mcp-server-value-picker

# Auto-detects transport mode
mcp-server-value-picker

# Force STDIO mode (for Claude Desktop)
mcp-server-value-picker --stdio

# Force HTTP mode
mcp-server-value-picker --http

To run directly without installing, use npx.

# Run via npx without installation
npx mcp-server-value-picker

Notes and configuration

Default HTTP endpoint is http://localhost:3456/mcp when you choose the HTTP transport. If you use STDIO transport, the tool communicates via standard input and output channels suitable for environments like Claude Desktop.

Files and structure

Key components include the server implementation, the UI view, and supporting styles. The project provides a ready-to-run example that wires a pick_value tool to the UI and demonstrates end-to-end interaction between the UI, host, and AI model.

Tools available

The test tool exposed by this server is the pick_value tool. It presents a UI with 10 selectable values and verifies that the host correctly forwards the selected value into the model context and handles follow-up messages.

Security and teardown

When you close or tear down the MCP server, ensure that your host handles teardown gracefully and that there are no lingering requests or errors. The test is designed to exercise teardown paths as part of the full lifecycle.

Available tools

pick_value

Displays 10 selectable values in the UI to verify that UI selections are correctly propagated to the model context and that the host can request the AI to identify the selected value via ui/message.