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io.modelcontext/clojure-sdk: Robust & Scalable MCP Server Development - MCP Implementation

io.modelcontext/clojure-sdk: Robust & Scalable MCP Server Development

Build MCP servers effortlessly with this Clojure SDK – robust, intuitive, and ready to scale. Developer-first design with client extensions on the horizon.

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About io.modelcontext/clojure-sdk

What is io.modelcontext/clojure-sdk: Robust & Scalable MCP Server Development?

io.modelcontext/clojure-sdk is a specialized Clojure framework designed to simplify the development of robust and scalable Model Context Protocol (MCP) servers. Built on industry-tested tools like lsp4clj, it provides a structured approach to creating servers that integrate seamlessly with platforms like Claude Desktop and MCP Inspector. This SDK abstracts complex JSON-RPC handling, allowing developers to focus on implementing business logic for tools, prompts, or analytical workflows.

How to use io.modelcontext/clojure-sdk: Robust & Scalable MCP Server Development?

Begin by adding the SDK dependency to your project:

{io.modelcontextprotocol/mcp-clojure-sdk
 :git/url "https://github.com/unravel-team/mcp-clojure-sdk.git"
 :git/sha "039cf220ac6bb3858f71e823016035e25"}

Build example servers using preconfigured templates for math operations, data visualization, or code analysis. Deploy configurations include path-specific JAR references and environment-specific JVM arguments for logging and performance tuning.

io.modelcontext/clojure-sdk Features

Key Features of io.modelcontext/clojure-sdk: Robust & Scalable MCP Server Development?

  • Pre-built server templates for rapid MVP development
  • Automatic JSON-RPC error handling via lsp4clj integration
  • Modular tool/prompt registration system
  • Production-ready logging via SLF4J with configurable levels
  • CI/CD pipeline support with versioned artifact generation

Use cases of io.modelcontext/clojure-sdk: Robust & Scalable MCP Server Development?

Common applications include:

  • Mathematical computation services (e.g., equation solving)
  • Data visualization pipelines using Vega-Lite specifications
  • Code analysis tools with custom diagnostic logic
  • Domain-specific prompt engines for specialized NLP tasks
  • Hybrid workflows combining server-side processing with LLM inference

io.modelcontext/clojure-sdk FAQ

FAQ from io.modelcontext/clojure-sdk: Robust & Scalable MCP Server Development?

  • How do I contribute? Submit PRs against the main branch and reference issues in todo.org
  • What platforms are supported? Works on JVM 17+, tested on Linux/macOS
  • Can I customize logging? Yes - override logback.xml in your deployment package
  • How is versioning managed? Semantic versioning with Clojars releases tagged in Git
  • Where's the API reference? Generated via clj-java-depstree in project documentation

Content

io.modelcontext/clojure-sdk

A clojure-sdk for creating Model Context Protocol servers!

Table of Contents :TOC_4:

  • io.modelcontext/clojure-sdk
    • Usage
      • Examples
        • Building the Examples Jar
        • Calculator: calculator_server
        • Vega-lite: vegalite_server
        • Code Analysis: code_analysis_server
    • Pending Work
    • Development of the SDK
    • Inspiration
    • License

Usage

The calculator_server.clj file and vegalite_server.clj file examples contains a full working code for defining an MCP server.

examples is a deps-new app project, and instructions for compiling and running the various example servers are in the examples/README.md file (also copied below this section)

The deps for clojure-sdk are:

{io.modelcontextprotocol/mcp-clojure-sdk
 {:git/url "https://github.com/unravel-team/mcp-clojure-sdk.git"
  :git/sha "039cf220ac6bb3858f71e823016035e257a5380d"}}

Examples

Building the Examples Jar

$ make clean && make examples-jar

The examples jar contains the following servers:

  1. Calculator: calculator_server
  2. Vega-lite: vegalite_server
  3. Code Analysis: code_analysis_server

Calculator: calculator_server

Provides basic arithmetic tools: add, subtract, multiply, divide, power, square-root, average, factorial

Some example commands you can try in Claude Desktop or Inspector:

  1. What's the average of [1, 2, 3, 4, 5]?
  2. What's the factorial of 15?
  3. What's 2 to the power of 1000?
  4. What's the square-root of 64?
Before running the calculator MCP server:

Remember:

  1. Use the full-path to the examples JAR on your system
In Claude Desktop
    "calculator": {
      "command": "java",
      "args": [
        "-Dclojure.tools.logging.factory=clojure.tools.logging.impl/log4j2-factory",
        "-Dorg.eclipse.jetty.util.log.class=org.eclipse.jetty.util.log.Slf4jLog",
        "-Dlog4j2.contextSelector=org.apache.logging.log4j.core.async.AsyncLoggerContextSelector",
        "-Dlog4j2.configurationFile=log4j2-mcp.xml",
        "-Dbabashka.json.provider=metosin/jsonista",
        "-Dlogging.level=INFO",
        "-cp",
        "/Users/vedang/mcp-clojure-sdk/examples/target/io.modelcontextprotocol.clojure-sdk/examples-1.2.0.jar",
        "calculator_server"
      ]
    }
In MCP Inspector
npx @modelcontextprotocol/inspector java -Dclojure.tools.logging.factory=clojure.tools.logging.impl/log4j2-factory -Dorg.eclipse.jetty.util.log.class=org.eclipse.jetty.util.log.Slf4jLog -Dlog4j2.contextSelector=org.apache.logging.log4j.core.async.AsyncLoggerContextSelector -Dlog4j2.configurationFile=log4j2-mcp.xml -Dbabashka.json.provider=metosin/jsonista -Dlogging.level=INFO -cp examples/target/io.modelcontextprotocol.clojure-sdk/examples-1.2.0.jar calculator_server

Vega-lite: vegalite_server

Provides tools for generating Vega-lite charts: save-data, visualize-data

PRE-REQUISITES: Needs vl-convert CLI to be installed.

Some example commands you can try in Claude Desktop or Inspector:

Here is some example data for you:

[
    { "year": 2011, "value": 14.6, "growth_type": "Market Cap Growth" },
    { "year": 2011, "value": 11.4, "growth_type": "Revenue Growth" },
    { "year": 2011, "value": 26.6, "growth_type": "Net Income Growth" },
    { "year": 2012, "value": 40.1, "growth_type": "Market Cap Growth" },
    { "year": 2012, "value": 42.7, "growth_type": "Revenue Growth" },
    { "year": 2012, "value": 36.9, "growth_type": "Net Income Growth" },
    { "year": 2013, "value": 16.9, "growth_type": "Market Cap Growth" },
    { "year": 2013, "value": 14.6, "growth_type": "Revenue Growth" },
    { "year": 2013, "value": 15.3, "growth_type": "Net Income Growth" },
    { "year": 2014, "value": 9.6, "growth_type": "Market Cap Growth" },
    { "year": 2014, "value": 7.9, "growth_type": "Revenue Growth" },
    { "year": 2014, "value": 10.9, "growth_type": "Net Income Growth" },
    { "year": 2015, "value": 5.8, "growth_type": "Market Cap Growth" },
    { "year": 2015, "value": 6.7, "growth_type": "Revenue Growth" },
    { "year": 2015, "value": 6.2, "growth_type": "Net Income Growth" },
    { "year": 2016, "value": -12.4, "growth_type": "Market Cap Growth" },
    { "year": 2016, "value": -3.9, "growth_type": "Revenue Growth" },
    { "year": 2016, "value": -32.2, "growth_type": "Net Income Growth" },
    { "year": 2017, "value": 25.3, "growth_type": "Market Cap Growth" },
    { "year": 2017, "value": 5.9, "growth_type": "Revenue Growth" },
    { "year": 2017, "value": 43.9, "growth_type": "Net Income Growth" }
]

Visualize this data for me using vega-lite.

Before running the vegalite MCP server

Remember:

  1. Replace the full-path to the examples JAR with the correct path on your system
  2. Specify the full-path to vl-convert on your system
In Claude Desktop
    "vegalite": {
      "command": "java",
      "args": [
        "-Dclojure.tools.logging.factory=clojure.tools.logging.impl/log4j2-factory",
        "-Dorg.eclipse.jetty.util.log.class=org.eclipse.jetty.util.log.Slf4jLog",
        "-Dlog4j2.contextSelector=org.apache.logging.log4j.core.async.AsyncLoggerContextSelector",
        "-Dlog4j2.configurationFile=log4j2-mcp.xml",
        "-Dbabashka.json.provider=metosin/jsonista",
        "-Dlogging.level=INFO",
        "-Dmcp.vegalite.vl_convert_executable=/Users/vedang/.cargo/bin/vl-convert",
        "-cp",
        "/Users/vedang/mcp-clojure-sdk/examples/target/io.modelcontextprotocol.clojure-sdk/examples-1.2.0.jar",
        "vegalite_server"
      ]
    }
In MCP Inspector

(Remember to use the full-path to the examples JAR on your system, or execute this command from the mcp-clojure-sdk repo)

npx @modelcontextprotocol/inspector java -Dclojure.tools.logging.factory=clojure.tools.logging.impl/log4j2-factory -Dorg.eclipse.jetty.util.log.class=org.eclipse.jetty.util.log.Slf4jLog -Dlog4j2.contextSelector=org.apache.logging.log4j.core.async.AsyncLoggerContextSelector -Dlog4j2.configurationFile=log4j2-mcp.xml -Dbabashka.json.provider=metosin/jsonista -Dlogging.level=INFO -Dmcp.vegalite.vl_convert_executable=/Users/vedang/.cargo/bin/vl-convert -cp examples/target/io.modelcontextprotocol.clojure-sdk/examples-1.2.0.jar vegalite_server

Code Analysis: code_analysis_server

This server is an example of a server which provides prompts and not tools. The following prompts are available: analyse-code and poem-about-code.

You can try the prompts out in Claude Desktop or Inspector. While these prompts are very basic, this is a good way to see how you could expose powerful prompts through this technique.

Before running the code-analysis MCP server

Remember:

  1. Replace the full-path to the examples JAR with the correct path on your system
In Claude Desktop
    "code-anaylsis": {
      "command": "java",
      "args": [
        "-Dclojure.tools.logging.factory=clojure.tools.logging.impl/log4j2-factory",
        "-Dorg.eclipse.jetty.util.log.class=org.eclipse.jetty.util.log.Slf4jLog",
        "-Dlog4j2.contextSelector=org.apache.logging.log4j.core.async.AsyncLoggerContextSelector",
        "-Dlog4j2.configurationFile=log4j2-mcp.xml",
        "-Dbabashka.json.provider=metosin/jsonista",
        "-Dlogging.level=INFO",
        "-cp",
        "/Users/vedang/mcp-clojure-sdk/examples/target/io.modelcontextprotocol.clojure-sdk/examples-1.2.0.jar",
        "code_analysis_server"
      ]
    }
In MCP Inspector

(Remember to use the full-path to the examples JAR on your system, or execute this command from the mcp-clojure-sdk repo)

npx @modelcontextprotocol/inspector java -Dclojure.tools.logging.factory=clojure.tools.logging.impl/log4j2-factory -Dorg.eclipse.jetty.util.log.class=org.eclipse.jetty.util.log.Slf4jLog -Dlog4j2.contextSelector=org.apache.logging.log4j.core.async.AsyncLoggerContextSelector -Dlog4j2.configurationFile=log4j2-mcp.xml -Dbabashka.json.provider=metosin/jsonista -Dlogging.level=INFO -cp examples/target/io.modelcontextprotocol.clojure-sdk/examples-1.2.0.jar code_analysis_server

Pending Work

You can help dear reader! Head over to the todo.org file to see the list of pending changes, arranged roughly in the order I plan to tackle them.

Development of the SDK

The clojure-sdk is a standard deps-new project, so you should expect all the deps-new commands to work as expected. Even so:

Run the project's tests:

$ make test ## or clojure -T:build test

Run the project's CI pipeline and build a JAR:

$ make build ## or clojure -T:build ci

This will produce an updated pom.xml file with synchronized dependencies inside the META-INF directory inside target/classes and the JAR in target. You can update the version (and SCM tag) information in generated pom.xml by updating build.clj.

Install it locally:

$ make install ## or clojure -T:build install

Deploy it to Clojars -- needs CLOJARS_USERNAME and CLOJARS_PASSWORD environment variables (requires the ci task be run first):

$ make deploy ## or clojure -T:build deploy

Your library will be deployed to io.modelcontext/clojure-sdk on clojars.org by default.

Inspiration

This SDK is built on top of lsp4clj, which solves the hard part of handling all the edge-cases of a JSON-RPC based server. I built this layer by hand and discovered all the edge-cases before realising that lsp4clj was the smarter approach. The code is super well written and easy to modify for my requirements.

License

Copyright © 2025 Unravel.tech

Distributed under the MIT License

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