Infracost MCP Server

Instructions

Implementation Reference

• src/cli.ts:178-217 (handler)

  Core handler function that constructs and executes the 'infracost comment' CLI command using child_process.execFile with the provided options.

  export async function executeComment(options: CommentOptions): Promise<CommandResult> {
    try {
      const args = ['comment', options.platform, '--path', resolve(options.path)];
  
      if (options.repo) {
        args.push('--repo', options.repo);
      }
  
      if (options.pullRequest) {
        args.push('--pull-request', options.pullRequest);
      }
  
      if (options.commit) {
        args.push('--commit', options.commit);
      }
  
      if (options.tag) {
        args.push('--tag', options.tag);
      }
  
      if (options.behavior) {
        args.push('--behavior', options.behavior);
      }
  
      const { stdout, stderr } = await execFileAsync('infracost', args, {
        maxBuffer: 10 * 1024 * 1024,
      });
  
      return {
        success: true,
        output: stdout,
        error: stderr || undefined,
      };
    } catch (error) {
      return {
        success: false,
        error: error instanceof Error ? error.message : 'Unknown error occurred',
      };
    }
  }

• src/tools.ts:52-63 (schema)

  Zod schema defining and validating the input parameters for the infracost_comment tool.

  export const CommentSchema = z.object({
    path: z.string().describe('Path to Infracost JSON file'),
    platform: z.enum(['github', 'gitlab', 'azure-repos', 'bitbucket']).describe('Git platform'),
    repo: z.string().optional().describe('Repository in format owner/repo'),
    pullRequest: z.string().optional().describe('Pull request number'),
    commit: z.string().optional().describe('Commit SHA'),
    tag: z.string().optional().describe('Tag for comment identification'),
    behavior: z
      .enum(['update', 'new', 'delete-and-new'])
      .optional()
      .describe('Comment behavior'),
  });

• src/tools.ts:382-404 (handler)

  Wrapper handler in InfracostTools class that checks for infracost CLI installation, calls executeComment, and formats MCP response.

  async handleComment(args: z.infer<typeof CommentSchema>) {
    const isInstalled = await checkInfracostInstalled();
    if (!isInstalled) {
      throw new Error(
        'Infracost CLI is not installed. Please install it from https://www.infracost.io/docs/'
      );
    }
  
    const result = await executeComment(args);
  
    if (!result.success) {
      throw new Error(result.error || 'Comment command failed');
    }
  
    return {
      content: [
        {
          type: 'text',
          text: result.output || 'Comment posted successfully',
        },
      ],
    };
  }

• src/index.ts:191-231 (registration)

  Tool registration in the ListTools response, defining name, description, and input schema for MCP server.

  {
    name: 'infracost_comment',
    description:
      'Post cost estimate comments to pull requests on GitHub, GitLab, Azure Repos, or Bitbucket. Automatically updates existing comments. Requires infracost CLI to be installed and appropriate platform credentials.',
    inputSchema: {
      type: 'object',
      properties: {
        path: {
          type: 'string',
          description: 'Path to Infracost JSON file',
        },
        platform: {
          type: 'string',
          enum: ['github', 'gitlab', 'azure-repos', 'bitbucket'],
          description: 'Git platform',
        },
        repo: {
          type: 'string',
          description: 'Repository in format owner/repo',
        },
        pullRequest: {
          type: 'string',
          description: 'Pull request number',
        },
        commit: {
          type: 'string',
          description: 'Commit SHA to associate comment with',
        },
        tag: {
          type: 'string',
          description: 'Tag for comment identification',
        },
        behavior: {
          type: 'string',
          enum: ['update', 'new', 'delete-and-new'],
          description: 'How to handle existing comments (default: update)',
        },
      },
      required: ['path', 'platform'],
    },
  },

• src/index.ts:724-727 (registration)

  Dispatch case in CallToolRequest handler that routes infracost_comment calls to tools.handleComment after schema validation.

  case 'infracost_comment': {
    const validatedArgs = CommentSchema.parse(args);
    return await tools.handleComment(validatedArgs);
  }