DNDzgz MCP Server

Instructions

Implementation Reference

• index.js:48-70 (handler)

  The handler function fetches tram station data from the API, computes the nearest stations using latitude and longitude, and returns JSON stringified nearest positions.

  async ({ latitude, longitude }) => {
    const response = await fetch("https://dndzgz.herokuapp.com/services/tram");
    if (response.ok) {
      const data = await response.json();
      const nearestPositions = getTopNearestPositions(
        data.locations,
        latitude,
        longitude
      );
      return {
        content: [{ type: "text", text: JSON.stringify(nearestPositions) }],
      };
    } else {
      return {
        content: [
          {
            type: "text",
            text: "It was not possible to get the tram stations",
          },
        ],
      };
    }
  }

• index.js:41-71 (registration)

  The tool is registered using server.tool() with name, description, input schema, and handler function.

  server.tool(
    "zaragoza-tram-stations",
    "Get all tram stations in Zaragoza",
    {
      latitude: z.number(),
      longitude: z.number(),
    },
    async ({ latitude, longitude }) => {
      const response = await fetch("https://dndzgz.herokuapp.com/services/tram");
      if (response.ok) {
        const data = await response.json();
        const nearestPositions = getTopNearestPositions(
          data.locations,
          latitude,
          longitude
        );
        return {
          content: [{ type: "text", text: JSON.stringify(nearestPositions) }],
        };
      } else {
        return {
          content: [
            {
              type: "text",
              text: "It was not possible to get the tram stations",
            },
          ],
        };
      }
    }
  );

• index.js:44-47 (schema)

  Zod schema defining input parameters: latitude and longitude as numbers.

  {
    latitude: z.number(),
    longitude: z.number(),
  },

• index.js:259-264 (helper)

  Helper function that gets the top N (default 10) nearest positions by calling getOrderedPositionsByDistance.

  function getTopNearestPositions(positions, latitude, longitude, size = 10) {
    return getOrderedPositionsByDistance(positions, latitude, longitude).slice(
      0,
      size
    );
  }

• index.js:281-297 (helper)

  Haversine distance calculation helper used to compute distances between coordinates for sorting nearest stations.

  function haversineDistanceInMeters(position1, position2) {
    const toRadians = (degrees) => degrees * (Math.PI / 180);
  
    const radiusOfEarth = 6371;
    const dLat = toRadians(position2.lat - position1.lat);
    const dLon = toRadians(position2.lon - position1.lon);
  
    const a =
      Math.sin(dLat / 2) * Math.sin(dLat / 2) +
      Math.cos(toRadians(position1.lat)) *
        Math.cos(toRadians(position2.lat)) *
        Math.sin(dLon / 2) *
        Math.sin(dLon / 2);
  
    const c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
    return radiusOfEarth * c * 1000;
  }