MJML MCP Server

Instructions

Implementation Reference

• index.js:296-335 (handler)

  Main execution logic for compile_mjml tool: parses args with schema, reads input file if needed, compiles MJML to HTML using mjml library with options, handles output saving, logs results and warnings, returns structured response.

  async handleCompileMjml(args) {
    const parsed = CompileMjmlSchema.parse(args);
    log.info('Compiling MJML', { template: parsed.template });
  
    const mjmlContent = await this.readInput(parsed.input, parsed.filePath);
  
    const mjmlOptions = {
      beautify: parsed.beautify,
      minify: parsed.minify,
      validationLevel: parsed.validationLevel,
      keepComments: parsed.keepComments,
      fonts: parsed.fonts || {},
    };
  
    const result = mjml(mjmlContent, mjmlOptions);
  
    if (result.errors.length > 0) {
      log.warn('MJML compilation completed with errors', result.errors);
    } else {
      log.info('MJML compilation successful');
    }
  
    const saveResult = await this.saveOutput(result.html, parsed.outputPath);
  
    return {
      content: [
        {
          type: 'text',
          text: JSON.stringify({
            success: true,
            html: result.html,
            errors: result.errors,
            warnings: result.warnings,
            mjmlOptions,
            saved: saveResult,
          }, null, 2),
        },
      ],
    };
  }

• index.js:35-44 (schema)

  Zod validation schema defining input parameters for the compile_mjml tool, including MJML input, formatting options, validation level, file handling flags, and output path.

  const CompileMjmlSchema = z.object({
    input: z.string().describe('MJML content or file path'),
    beautify: z.boolean().optional().default(true).describe('Beautify the output HTML'),
    minify: z.boolean().optional().default(false).describe('Minify the output HTML'),
    validationLevel: z.enum(['skip', 'soft', 'strict']).optional().default('soft').describe('Validation level'),
    filePath: z.boolean().optional().default(false).describe('Treat input as file path'),
    keepComments: z.boolean().optional().default(false).describe('Keep comments in output'),
    fonts: z.record(z.string()).optional().describe('Custom fonts configuration'),
    outputPath: z.string().optional().describe('Save compiled HTML to file path'),
  });

• index.js:137-184 (registration)

  Tool registration in ListToolsRequestHandler: defines name 'compile_mjml', description, and detailed inputSchema matching the Zod schema for MCP protocol compliance.

  {
    name: 'compile_mjml',
    description: 'Compile MJML to HTML with various options',
    inputSchema: {
      type: 'object',
      properties: {
        input: {
          type: 'string',
          description: 'MJML content or file path',
        },
        beautify: {
          type: 'boolean',
          description: 'Beautify the output HTML',
          default: true,
        },
        minify: {
          type: 'boolean',
          description: 'Minify the output HTML',
          default: false,
        },
        validationLevel: {
          type: 'string',
          enum: ['skip', 'soft', 'strict'],
          description: 'Validation level',
          default: 'soft',
        },
        filePath: {
          type: 'boolean',
          description: 'Treat input as file path',
          default: false,
        },
        keepComments: {
          type: 'boolean',
          description: 'Keep comments in output',
          default: false,
        },
        fonts: {
          type: 'object',
          description: 'Custom fonts configuration',
        },
        outputPath: {
          type: 'string',
          description: 'Save compiled HTML to file path',
        },
      },
      required: ['input'],
    },
  },

• index.js:98-114 (helper)

  Helper method used by handler to read MJML input from string or file path, with error handling for file access.

  async readInput(input, isFilePath) {
    if (isFilePath) {
      try {
        const fullPath = resolve(input);
        await access(fullPath);
        const content = await readFile(fullPath, 'utf-8');
        log.debug(`Read file: ${fullPath}`);
        return content;
      } catch (error) {
        throw new McpError(
          ErrorCode.InvalidRequest,
          `Failed to read MJML file: ${error.message}`
        );
      }
    }
    return input;
  }

• index.js:116-131 (helper)

  Helper method used by handler to optionally save compiled HTML to output file path, returns save status.

  async saveOutput(content, outputPath) {
    if (outputPath) {
      try {
        const fullPath = resolve(outputPath);
        await writeFile(fullPath, content, 'utf-8');
        log.info(`Output saved to: ${fullPath}`);
        return { saved: true, path: fullPath };
      } catch (error) {
        throw new McpError(
          ErrorCode.InternalError,
          `Failed to save output: ${error.message}`
        );
      }
    }
    return { saved: false };
  }