PostGIS MCP Server

Instructions

Implementation Reference

• server.ts:1567-1620 (handler)

  Handler for the 'simplify-geometry' tool. Parses input using SimplifyGeometrySchema, determines simplify function (ST_Simplify or ST_SimplifyPreserveTopology), executes PostGIS query to simplify geometry, computes metrics like point count and area before/after, and returns detailed JSON response including reduction ratio.

  case "simplify-geometry": {
    const { geometry_wkt, tolerance, preserve_collapsed } =
      SimplifyGeometrySchema.parse(args);
  
    const simplifyFunc = preserve_collapsed
      ? "ST_SimplifyPreserveTopology"
      : "ST_Simplify";
  
    const result = await client.query(
      `
      SELECT 
        ST_AsText(${simplifyFunc}(ST_GeomFromText($1), $2)) as simplified_wkt,
        ST_AsGeoJSON(${simplifyFunc}(ST_GeomFromText($1), $2)) as simplified_geojson,
        ST_NumPoints(ST_GeomFromText($1)) as original_points,
        ST_NumPoints(${simplifyFunc}(ST_GeomFromText($1), $2)) as simplified_points,
        ST_Area(ST_GeomFromText($1)::geography) as original_area,
        ST_Area(${simplifyFunc}(ST_GeomFromText($1), $2)::geography) as simplified_area
    `,
      [geometry_wkt, tolerance]
    );
  
    return {
      content: [
        {
          type: "text",
          text: JSON.stringify(
            {
              input_geometry: geometry_wkt,
              tolerance: tolerance,
              preserve_collapsed: preserve_collapsed,
              simplified_wkt: result.rows[0].simplified_wkt,
              simplified_geojson: JSON.parse(
                result.rows[0].simplified_geojson
              ),
              original_points: result.rows[0].original_points,
              simplified_points: result.rows[0].simplified_points,
              original_area_sqmeters:
                parseFloat(result.rows[0].original_area) || 0,
              simplified_area_sqmeters:
                parseFloat(result.rows[0].simplified_area) || 0,
              reduction_ratio:
                result.rows[0].original_points > 0
                  ? 1 -
                    result.rows[0].simplified_points /
                      result.rows[0].original_points
                  : 0,
            },
            null,
            2
          ),
        },
      ],
    };
  }

• server.ts:88-92 (schema)

  Zod input schema for 'simplify-geometry' tool validating geometry_wkt (string), tolerance (number), and optional preserve_collapsed (boolean). Used for parsing arguments in the handler.

  const SimplifyGeometrySchema = z.object({
    geometry_wkt: z.string(),
    tolerance: z.number(),
    preserve_collapsed: z.boolean().optional().default(false),
  });

• server.ts:752-772 (registration)

  Tool registration in ListToolsRequestHandler, defining name, description, and JSON inputSchema matching the Zod schema for client tool listing.

    name: "simplify-geometry",
    description: "Geometriyi basitleştir (Douglas-Peucker algoritması)",
    inputSchema: {
      type: "object",
      properties: {
        geometry_wkt: {
          type: "string",
          description: "WKT formatında geometri",
        },
        tolerance: {
          type: "number",
          description: "Basitleştirme toleransı",
        },
        preserve_collapsed: {
          type: "boolean",
          description: "Çöken geometrileri koru",
        },
      },
      required: ["geometry_wkt", "tolerance"],
    },
  },