get_rent_index

Instructions

Implementation Reference

• src/modules/realestate.ts:314-394 (handler)

  The handleGetRentIndex function performs the logic of fetching and formatting the Swiss Consumer Price Index data.

  async function handleGetRentIndex(args: Record<string, unknown>): Promise<string> {
    const rawYear = typeof args.year === "number" ? args.year : undefined;
    const rawLimit = Math.min(60, Math.max(1, typeof args.limit === "number" ? args.limit : 24));
  
    // Fetch CPI (LIK) data from Canton Zug open data - monthly index (base Dec 1982 = 100)
    // This is the Swiss national CPI (Landesindex der Konsumentenpreise) which includes
    // the residential rent component
    const totalRecords = 515; // approximate total
  
    let url: string;
    if (rawYear !== undefined) {
      // Fetch specific year - estimate offset
      // Data starts from Dec 1982 (record 0) ~ month 0
      // Each year has 12 records. 1982 has 1 record (Dec only).
      const yearsFromStart = rawYear - 1982;
      const estOffset = Math.max(0, 1 + (yearsFromStart - 1) * 12);
      url = buildUrl(CPI_RENT_URL, { _limit: 12, _offset: estOffset });
    } else {
      // Latest data - fetch last N months
      const offset = Math.max(0, totalRecords - rawLimit);
      url = buildUrl(CPI_RENT_URL, { _limit: rawLimit, _offset: offset });
    }
  
    const data = await fetchJSON<ZgCpiResponse>(url, {
      headers: { "User-Agent": "mcp-swiss" },
    });
  
    // Filter by year if specified
    let rows = data.results;
    if (rawYear !== undefined) {
      rows = rows.filter((r) => r.jahr === String(rawYear));
    }
  
    if (rows.length === 0 && rawYear !== undefined) {
      throw new Error(
        `No CPI data found for year ${rawYear}. Available data: 1982–2025.`
      );
    }
  
    const series = rows.map((r) => ({
      year: parseInt(r.jahr, 10),
      month: r.monat,
      index: parseFloat(r.index),
    }));
  
    const latestRow = series[series.length - 1];
    const firstRow = series[0];
  
    // YoY change (if we have 12+ months)
    let yoyChange: number | null = null;
    if (series.length >= 13) {
      const prev = series[series.length - 13];
      if (prev) {
        yoyChange = parseFloat(
          (((latestRow.index - prev.index) / prev.index) * 100).toFixed(2)
        );
      }
    }
  
    const period =
      series.length > 0
        ? `${firstRow.month} ${firstRow.year} – ${latestRow.month} ${latestRow.year}`
        : "N/A";
  
    return JSON.stringify({
      index_name: "Swiss Consumer Price Index (LIK / IPC)",
      baseline: "December 1982 = 100",
      note:
        "The Swiss CPI (Landesindex der Konsumentenpreise) tracks the cost of living including residential rents. " +
        "This is the official Swiss national index published by BFS/FSO. " +
        "For the residential property price index (buying/ownership), use get_property_price_index.",
      period,
      latest: latestRow ?? null,
      data_points: series.length,
      series,
      yoy_change_percent: yoyChange,
      source: "Federal Statistical Office (BFS) via Canton Zug Open Data",
      source_url: "https://data.zg.ch/store/1/resource/334",
      ckan_dataset: "https://opendata.swiss/en/dataset/landesindex-der-konsumentenpreise",
    });
  }

• src/modules/realestate.ts:453-473 (schema)

  The definition of get_rent_index containing the name, description, and inputSchema.

    name: "get_rent_index",
    description:
      "Get the Swiss Consumer Price Index (CPI/LIK), which tracks cost of living including " +
      "residential rents. Baseline December 1982 = 100. Published monthly by BFS. " +
      "For property purchase prices, use get_property_price_index instead.",
    inputSchema: {
      type: "object",
      properties: {
        year: {
          type: "number",
          description:
            "Filter to a specific year (1983–2025). Omit for latest 24 months.",
        },
        limit: {
          type: "number",
          description:
            "Number of recent monthly data points to return (1–60, default 24). Ignored if year is set.",
        },
      },
    },
  },

• src/modules/realestate.ts:487-488 (registration)

  Registration of the get_rent_index tool in the main dispatcher within handleRealEstate function.

  case "get_rent_index":
    return handleGetRentIndex(args);