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MCP Test Servers

by msfeldstein

Development/TestingTest ServerAPIDevelopment

A collection of test servers implementing the Model Context Protocol (MCP). These servers provide various functionalities and edge cases for testing MCP clients.

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Last updated: N/A

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