MCP Test Servers

A collection of test servers implementing the Model Context Protocol (MCP).

Available Servers

• ping: A simple server that responds with 'pong'
• resource: Resource server implementation
• combined: Combined server implementation
• broken-tool: Server with intentionally broken tool
• crash-on-startup: Server that crashes on startup
• env-check: Server for environment checking
• env-echo: Server that echoes environment variables
• many-resources: Server with multiple resources
• duplicate-names: Server with duplicate name implementations
• image: Server for image handling
• big-response: Server that returns large responses
• date: Server for date operations
• time: Server that returns the current time in ISO format
• many-tools: Server with 100 tools that each return 'ack'
• named: Server with configurable name via MCP_SERVER_NAME environment variable
• bad-param: Server with an intentionally malformed parameter name
• stderr: Server that logs to stderr
• optional-param: Server with optional parameters

Usage

To run a server, use:

npx @msfeldstein/mcp-test-servers <server-type>

Example:

npx @msfeldstein/mcp-test-servers time

For the named server, you can set a custom name using the MCP_SERVER_NAME environment variable:

MCP_SERVER_NAME="my-custom-server" npx @msfeldstein/mcp-test-servers named

Server Details

Ping Server

The ping server provides a simple ping-pong interaction:

• Tool: ping
• Returns: "pong"
• No parameters required

Resource Server

The resource server provides a single text resource:

• Resource name: "Hello World Text"
• URI: "test://hello.txt"
• Content: "Hello, world"
• MIME type: "text/plain"

Combined Server

The combined server implements both tool and resource capabilities:

• Tool: ping - Returns "pong"
• Tool: fizzbuzz - Generates a FIZZY sequence up to the specified number
• Resource: "Hello World Text" - Same as resource server

Broken Tool Server

The broken tool server intentionally throws an error when the tool is called:

• Tool: crash
• Behavior: Throws an error with message "This tool is intentionally broken!"

Crash on Startup Server

This server crashes during initialization, useful for testing error handling.

Environment Check Server

The env-check server requires an environment variable to run:

• Environment variable: SHOULD_RUN=true (required)
• Tool: status
• Returns: "Server is running with SHOULD_RUN=true"

Environment Echo Server

The env-echo server returns all environment variables:

• Tool: echo_env
• Returns: A formatted list of all environment variables

Many Resources Server

The many-resources server provides multiple resources (600):

• Resources: "Resource 1" through "Resource 600"
• Each has unique content and URI

Duplicate Names Server

The duplicate-names server provides resources with duplicate names:

• Three sets of resources with names "Common Resource", "Duplicate File", and "Same Name Different Content"
• Each name has 3 versions with different content and URIs

Image Server

The image server provides an image resource:

• Tool: generate_image
• Returns: A red circle image in base64 format

Big Response Server

The big-response server can generate large responses:

• Tool: generate_big_response
• Parameter: stringLength - The length of the random string to generate
• Returns: A random string of the specified length

Date Server

The date server provides date operations:

• Tool: Provides date operations (details may vary)

Time Server

The time server provides a simple tool to get the current time:

• Tool: get-time
• Returns: Current time in ISO format
• No parameters required

Many Tools Server

The many tools server provides 100 simple tools:

• Tools: tool_1 through tool_100
• Each tool returns: 'ack'
• No parameters required

Named Server

The named server allows testing with custom server names:

• Tool: <server-name>_get_name (e.g., "my-custom-server_get_name")
• Returns: The server's configured name
• No parameters required
• Name can be set via MCP_SERVER_NAME environment variable
• Defaults to 'unnamed-server' if no name is provided

Bad Param Server

The bad-param server includes a tool with an incorrectly formed parameter name:

• Tool: bad-param
• Parameter: Has an invalid parameter name with special characters
• Useful for testing how clients handle malformed parameter definitions

Stderr Server

The stderr server demonstrates stderr logging:

• Tool: log-to-stderr
• Behavior: Logs a message to stderr while responding
• Returns: "Should have logged to stderr"
• No parameters required

Optional Param Server

The optional-param server demonstrates parameter optionality:

• Tool: echo
• Parameters:
  • name (required): The name of the caller
  • text (optional): The text to echo
• Returns: The provided text or "No message sent" if no text was provided