MCP Server

The MCP (Model Context Protocol) Server Plugin for Jenkins implements the server-side component of the Model Context Protocol. This plugin enables Jenkins to act as an MCP server, providing context, tools, and capabilities to MCP clients, such as LLM-powered applications or IDEs.

• MCP Server Implementation: Implements the server-side of the Model Context Protocol.
• Jenkins Integration: Exposes Jenkins functionalities as MCP tools and resources.
• Extensible Architecture: Allows easy extension of MCP capabilities through the McpServerExtension interface.

1. Endpoint: The main entry point for MCP communication, handling MCP transport connections and message routing.
2. DefaultMcpServer: Implements McpServerExtension, providing default tools for interacting with Jenkins jobs and builds.
3. McpToolWrapper: Wraps Java methods as MCP tools, handling parameter parsing and result formatting.
4. McpServerExtension: Interface for extending MCP server capabilities.

This MCP Server is based on the MCP Java SDK version 0.11.0, which implements the MCP specification version 2025-03-26.

• Jenkins (version 2.479 or higher)

The MCP Server plugin automatically sets up necessary endpoints and tools upon installation, requiring no additional configuration.

The following system properties can be used to configure the MCP Server plugin:

• hard limit on max number of log lines to return with io.jenkins.plugins.mcp.server.extensions.BuildLogsExtension.limit.max=10000 (default 10000)

MCP clients can connect to the server using:

• Streamable HTTP Endpoint: <jenkins-url>/mcp-server/mcp
• SSE Endpoint: <jenkins-url>/mcp-server/sse
• Message Endpoint: <jenkins-url>/mcp-server/message

The MCP Server Plugin requires the same credentials as the Jenkins instance it's running on. To authenticate your MCP queries:

1. Jenkins API Token: Generate an API token from your Jenkins user account.
2. Basic Authentication: Use the API token in the HTTP Basic Authentication header.

{
  "mcpServers": {
    "jenkins": {
      "autoApprove": [
        
      ],
      "disabled": false,
      "timeout": 60,
      "type": "streamableHttp",
      "url": "https://jenkins-host/mcp-server/mcp",
      "headers": {
        "Authorization": "Basic <user:token base64>"
      }
    }
  }
}

Copilot doesn't work well with the Streamable transport as of now, and I'm still investigating the issues. Please continue to use the SSE endpoint.

{
  "mcp": {
    "servers": {
      "jenkins": {
        "type": "sse",
        "url": "https://jenkins-host/mcp-server/sse",
        "headers": {
          "Authorization": "Basic <user:token base64>"
        }
      }
    }
  }
}

{
  "servers": {
    "jenkins": {
      "command": "npx",
      "args": [
        "mcp-remote",
        "http://jenkins-host/mcp-server/mcp",
        "--header",
        "Authorization: Bearer ${AUTH_TOKEN}"
      ],
      "env": {
        "AUTH_TOKEN": "Basic <user:token base64>"
      }
    }
  }
}

The plugin provides the following built-in tools for interacting with Jenkins:

• getJob: Get a Jenkins job by its full path.

• getJobs: Get a paginated list of Jenkins jobs, sorted by name.

• triggerBuild: Trigger a build of a job. This tool supports parameterized builds. You can provide parameters as a JSON object where each key is the parameter name. For example:

  {
    "jobFullName": "my-job",
    "parameters": {
      "BRANCH": "main",
      "DEBUG_MODE": "true"
    }
  }

  Note on Parameters:

  • Only built-in parameter types in core Jenkins are fully supported.
  • Unsupported parameter types will be ignored and set as null in the pipeline.
  • File parameters are not currently supported.
  • If you encounter a parameter type from a Jenkins plugin that is not supported, please create an issue in our repository.

• getBuild: Retrieve a specific build or the last build of a Jenkins job.
• updateBuild: Update build display name and/or description.
• getBuildLog: Retrieve log lines with pagination for a specific build or the last build.

• getJobScm: Retrieve SCM configurations of a Jenkins job.
• getBuildScm: Retrieve SCM configurations of a specific build.
• getBuildChangeSets: Retrieve change log sets of a specific build.

• whoAmI: Get information about the current user.

Each tool accepts specific parameters to customize its behavior. For detailed usage instructions and parameter descriptions, refer to the API documentation or use the MCP introspection capabilities.

To use these tools, connect to the MCP server endpoint and make tool calls using your MCP client implementation.

To add new MCP tools or functionalities:

1. Create a class implementing McpServerExtension.
2. Use @Tool to expose methods as MCP tools.
3. Use @ToolParam to define and describe tool parameters.

Example:

@Extension
public class MyCustomMcpExtension implements McpServerExtension {
	@Tool(description = "My custom tool")
	public String myCustomTool(@ToolParam(description = "Input parameter") String input) {
		// Tool implementation
	}
}

The MCP Server Plugin handles various result types with the following approach:

• List Results: Each element in the list is converted to a separate text content item in the response.
• Single Objects: The entire object is converted into a single text content item.

For serialization to text content:

• @ExportedBean Annotation: If the result object is annotated with @ExportedBean (from org.kohsuke.stapler.export), Jenkins' org.kohsuke.stapler.export.Flavor.JSON exporting mechanism is used.
• Other Objects: For objects without the @ExportedBean annotation, Jackson is used for JSON serialization.

This approach ensures flexible and efficient handling of different result types, accommodating both Jenkins-specific exported objects and standard Java objects. This flexible approach ensures that tool results are consistently and accurately represented in the MCP response, regardless of their complexity.

The MCP Server Plugin seamlessly integrates with GitHub Copilot, enhancing your development experience by providing direct access to Jenkins information within your IDE. This integration allows you to interact with Jenkins jobs and builds using natural language queries.

As shown in the screenshot:

1. You can ask Copilot about Jenkins jobs using natural language, e.g., "list jenkins job under root".
2. Copilot uses the MCP Server to fetch and display information about Jenkins jobs, listing the jobs under the root directory.
3. You can also request specific information, such as "get the last build status of job a", and Copilot will provide the relevant details including build number, status, and URL.

This integration streamlines your workflow by allowing you to access Jenkins information without leaving your development environment.

For more details on the Model Context Protocol and its Java SDK:

• MCP Introduction
• MCP Java SDK Server Component

Contributions to the MCP Server plugin are welcome. Please refer to the Jenkins contribution guidelines for more information.

This project is licensed under the MIT License - see the LICENSE file for details.