fetch_rss_feed

Instructions

Implementation Reference

• src/index.ts:32-73 (handler)

  Execute handler for fetch_rss_feed tool: handles caching, calls rssReader.fetchFeed, and returns structured JSON.

  execute: async (args, context) => {
    try {
      logger.info(`Fetching RSS feed: ${args.url}`);
  
      // Check cache first
      const cached = feedCache.get(args.url);
      if (cached) {
        logger.debug(`Returning cached feed: ${args.url}`);
        return JSON.stringify(cached, null, 2);
      }
  
      // Get cache metadata for conditional requests
      const cacheMeta = feedCache.getMetadata(args.url);
  
      // Fetch feed
      const result = await rssReader.fetchFeed(args.url, {
        useDescriptionAsContent: args.useDescriptionAsContent === 'true',
        etag: cacheMeta?.etag,
        lastModified: cacheMeta?.lastModified,
      });
  
      // Cache the result
      feedCache.set(args.url, result);
  
      logger.info(
        `Successfully fetched feed: ${args.url}, ${result.items.length} items`
      );
      return JSON.stringify(result, null, 2);
    } catch (error: any) {
      if (error.message === "NOT_MODIFIED" && feedCache.has(args.url)) {
        // Return cached version if not modified
        const cached = feedCache.get(args.url);
        if (cached) {
          logger.debug(`Feed not modified, returning cache: ${args.url}`);
          return JSON.stringify(cached, null, 2);
        }
      }
  
      logger.error(`Failed to fetch RSS feed ${args.url}: ${error.message}`);
      throw new UserError(`Failed to fetch RSS feed: ${error.message}`);
    }
  },

• src/index.ts:17-25 (schema)

  Zod schema defining input parameters for fetch_rss_feed tool.

  const FetchRssFeedSchema = z.object({
    url: z.string().describe("The URL of the RSS feed to fetch"),
    useDescriptionAsContent: z
      .string()
      .optional()
      .describe(
        "If 'true', use description field as content instead of content field"
      ),
  });

• src/index.ts:27-74 (registration)

  Registration of the fetch_rss_feed tool with FastMCP server, including name, description, schema, and execute handler.

  server.addTool({
    name: "fetch_rss_feed",
    description:
      "Fetches and parses an RSS feed, returning structured data with feed info and items",
    parameters: FetchRssFeedSchema,
    execute: async (args, context) => {
      try {
        logger.info(`Fetching RSS feed: ${args.url}`);
  
        // Check cache first
        const cached = feedCache.get(args.url);
        if (cached) {
          logger.debug(`Returning cached feed: ${args.url}`);
          return JSON.stringify(cached, null, 2);
        }
  
        // Get cache metadata for conditional requests
        const cacheMeta = feedCache.getMetadata(args.url);
  
        // Fetch feed
        const result = await rssReader.fetchFeed(args.url, {
          useDescriptionAsContent: args.useDescriptionAsContent === 'true',
          etag: cacheMeta?.etag,
          lastModified: cacheMeta?.lastModified,
        });
  
        // Cache the result
        feedCache.set(args.url, result);
  
        logger.info(
          `Successfully fetched feed: ${args.url}, ${result.items.length} items`
        );
        return JSON.stringify(result, null, 2);
      } catch (error: any) {
        if (error.message === "NOT_MODIFIED" && feedCache.has(args.url)) {
          // Return cached version if not modified
          const cached = feedCache.get(args.url);
          if (cached) {
            logger.debug(`Feed not modified, returning cache: ${args.url}`);
            return JSON.stringify(cached, null, 2);
          }
        }
  
        logger.error(`Failed to fetch RSS feed ${args.url}: ${error.message}`);
        throw new UserError(`Failed to fetch RSS feed: ${error.message}`);
      }
    },
  });

• src/services/rss-reader.ts:156-189 (helper)

  Core RSS feed fetching logic in RSSReader class: fetches raw XML, parses it, formats into structured FeedResult.

  async fetchFeed(
    url: string,
    options?: {
      useDescriptionAsContent?: boolean;
      etag?: string;
      lastModified?: string;
    }
  ): Promise<FeedResult> {
    // Fetch raw feed
    const { data, etag, lastModified, notModified } = await this.fetchRawFeed(
      url,
      options?.etag,
      options?.lastModified
    );
    
    if (notModified) {
      throw new Error('NOT_MODIFIED');
    }
    
    // Parse feed
    const parsed = await this.parseFeed(data);
    if (!parsed) {
      throw new Error('Failed to parse feed XML');
    }
    
    // Format feed
    const result = this.formatFeed(parsed, url, options?.useDescriptionAsContent);
    
    // Add cache headers if available
    if (etag) result.etag = etag;
    if (lastModified) result.lastModified = lastModified;
    
    return result;
  }

• src/types.ts:80-83 (schema)

  TypeScript interface matching the input parameters for fetch_rss_feed.

  export interface FetchRssFeedParams {
    url: string;
    useDescriptionAsContent?: 'true' | 'false';
  }