Visa Design System MCP Server

Instructions

Implementation Reference

• src/services/guidelines-service.ts:74-104 (handler)

  Core handler function that executes the tool logic: validates ID, retrieves from cache, handles errors, returns the Guideline object.

  async getGuideline(id: string): Promise<Guideline> {
    return this.circuitBreaker.execute(async () => {
      if (!id || typeof id !== 'string') {
        throw new ValidationError('Guideline ID must be a non-empty string', [], 
          { service: 'GuidelinesService', method: 'getGuideline', id });
      }
  
      const cachedData = this.dataManager.getCachedData();
      
      if (!cachedData) {
        throw new DataError('No guidelines data available', [
          'Ensure data files are loaded',
          'Check data directory configuration'
        ], { service: 'GuidelinesService', method: 'getGuideline' });
      }
  
      const guideline = cachedData.guidelines.find(
        guide => guide.id.toLowerCase() === id.toLowerCase()
      );
  
      if (!guideline) {
        const availableGuidelines = cachedData.guidelines.map(guide => guide.id);
        throw new NotFoundError('Guideline', id, [
          `Available guidelines: ${availableGuidelines.join(', ')}`,
          'Check guideline ID spelling'
        ], { service: 'GuidelinesService', method: 'getGuideline' });
      }
  
      return guideline;
    }, { service: 'GuidelinesService', method: 'getGuideline', id });
  }

• src/mcp-server.ts:564-584 (handler)

  MCP protocol handler that validates arguments, calls the guidelines service, and formats the response as CallToolResult.

  private async handleGetGuidelineDetails(args: Record<string, any>): Promise<CallToolResult> {
    const { id } = args;
    
    if (!id || typeof id !== 'string') {
      throw new McpError(
        ErrorCode.InvalidParams,
        'Guideline ID is required and must be a string'
      );
    }
  
    const guideline = await this.guidelinesService.getGuideline(id);
  
    return {
      content: [
        {
          type: 'text',
          text: JSON.stringify(guideline, null, 2)
        }
      ]
    };
  }

• src/types/index.ts:54-63 (schema)

  Type definition for the Guideline object returned by the tool.

  export interface Guideline {
    id: string;
    title: string;
    category: string;
    content: string;
    tags: string[];
    lastUpdated: Date;
    relatedComponents?: string[];
    relatedTokens?: string[];
  }

• src/mcp-server.ts:246-258 (registration)

  Tool registration including name, description, and input schema in the getToolDefinitions() method.

    name: 'get-guideline-details',
    description: 'Get detailed information about a specific guideline',
    inputSchema: {
      type: 'object',
      properties: {
        id: {
          type: 'string',
          description: 'Guideline ID'
        }
      },
      required: ['id']
    }
  },

• src/mcp-server.ts:312-313 (registration)

  Dispatch case in handleToolCall switch statement that routes to the specific handler.

  case 'get-guideline-details':
    return await this.handleGetGuidelineDetails(args);