clj-kondo MCP Server

Instructions

Implementation Reference

• src/index.ts:79-127 (handler)

  CallToolRequestSchema handler that dispatches to lint_clojure tool by validating arguments and executing clj-kondo CLI.

  this.server.setRequestHandler(CallToolRequestSchema, async (request: Request) => {
    if (!request.params || request.params.name !== 'lint_clojure') {
      throw new McpError(
        ErrorCode.MethodNotFound,
        `Unknown tool: ${request.params?.name || 'undefined'}`
      );
    }
  
    if (!request.params.arguments || !isValidLintArgs(request.params.arguments)) {
      throw new McpError(
        ErrorCode.InvalidParams,
        'Invalid lint arguments'
      );
    }
  
    try {
      const configDirArg = request.params.arguments.configDir
        ? `--config-dir "${request.params.arguments.configDir}"`
        : '';
      const levelArg = request.params.arguments.level === 'warning'
        ? '--fail-level error'
        : '--fail-level warning';
      const { stdout, stderr } = await execAsync(
        `clj-kondo --lint "${request.params.arguments.file}" ${configDirArg} ${levelArg} --parallel`
      );
  
      return {
        content: [
          {
            type: 'text',
            text: stdout || stderr,
          },
        ],
      };
    } catch (error: any) {
      // clj-kondo returns non-zero exit code when it finds linting issues
      if (error.stdout || error.stderr) {
        return {
          content: [
            {
              type: 'text',
              text: error.stdout || error.stderr,
            },
          ],
        };
      }
      throw error;
    }
  });

• src/index.ts:56-74 (schema)

  Input schema definition for the lint_clojure tool.

  inputSchema: {
    type: 'object',
    properties: {
      file: {
        type: 'string',
        description: 'Can be: 1) Absolute path to a file, 2) Directory path (will lint all .clj/.cljs/.cljc files recursively), or 3) Classpath string (obtained via `lein classpath` or `clojure -Spath`)',
      },
      configDir: {
        type: 'string',
        description: 'Optional absolute path to .clj-kondo config directory (e.g. /Users/name/project/.clj-kondo). If not provided, clj-kondo will look for .clj-kondo directory in the current and parent directories.',
      },
      level: {
        type: 'string',
        enum: ['warning'],
        description: 'Optional linting level. By default all lints are errors. Set to "warning" to use warning level instead.',
      }
    },
    required: ['file'],
  },

• src/index.ts:53-75 (registration)

  Tool registration in the ListToolsRequestSchema handler.

  {
    name: 'lint_clojure',
    description: 'Lint Clojure/ClojureScript/EDN content using clj-kondo',
    inputSchema: {
      type: 'object',
      properties: {
        file: {
          type: 'string',
          description: 'Can be: 1) Absolute path to a file, 2) Directory path (will lint all .clj/.cljs/.cljc files recursively), or 3) Classpath string (obtained via `lein classpath` or `clojure -Spath`)',
        },
        configDir: {
          type: 'string',
          description: 'Optional absolute path to .clj-kondo config directory (e.g. /Users/name/project/.clj-kondo). If not provided, clj-kondo will look for .clj-kondo directory in the current and parent directories.',
        },
        level: {
          type: 'string',
          enum: ['warning'],
          description: 'Optional linting level. By default all lints are errors. Set to "warning" to use warning level instead.',
        }
      },
      required: ['file'],
    },
  },

• src/index.ts:16-23 (helper)

  Helper function to validate input arguments for lint_clojure.

  const isValidLintArgs = (
    args: any
  ): args is { file: string; configDir?: string; level?: 'warning' } =>
    typeof args === 'object' &&
    args !== null &&
    typeof args.file === 'string' &&
    (args.configDir === undefined || typeof args.configDir === 'string') &&
    (args.level === undefined || args.level === 'warning');