LINE Bot MCP Server

Instructions

Implementation Reference

• src/tools/queryMssql.ts:46-63 (handler)

  The handler function for the 'query_mssql' tool. It executes a read-only SQL query using the queryReadOnly helper, slices the rows to the specified limit, truncates large JSON previews, and returns a structured success response with columns, row count, and preview rows, or an error response.

  async ({ sql, params, limit, maxChars }) => {
    try {
      const { rows, columns } = await queryReadOnly(sql, params);
      const sliced = rows.slice(0, limit);
      const payload = { columns, rowCount: rows.length, rows: sliced };
      let text = JSON.stringify(payload);
      if (text.length > maxChars) {
        text = text.slice(0, maxChars) + "... (truncated)";
      }
      return createSuccessResponse({
        columns,
        rowCount: rows.length,
        rows: sliced,
      });
    } catch (e: any) {
      return createErrorResponse(`MSSQL query failed: ${e?.message || e}`);
    }
  },

• src/tools/queryMssql.ts:12-36 (schema)

  Zod schemas defining the input parameters for the query_mssql tool: sql (string), params (optional record), limit (number 1-500 default 100), maxChars (number 1000-200000 default 12000).

  const sqlSchema = z
    .string()
    .min(1)
    .describe(
      "Read-only SQL beginning with SELECT or WITH. Parameters as @name.",
    );
  const paramsSchema = z
    .record(z.any())
    .optional()
    .describe("Key-value parameters for @name placeholders in SQL.");
  const limitSchema = z
    .number()
    .int()
    .min(1)
    .max(500)
    .default(100)
    .describe("Maximum rows to return (client-side slice).");
  const maxCharsSchema = z
    .number()
    .int()
    .min(1000)
    .max(200000)
    .default(12000)
    .describe("Max characters in serialized preview.");

• src/index.ts:76-76 (registration)

  Top-level registration of the QueryMssql tool instance on the MCP server in the main index file.

  new QueryMssql().register(server);

• src/common/db/mssql.ts:62-80 (helper)

  Core helper function that validates the SQL is read-only SELECT/WITH, connects to the MSSQL connection pool, binds parameters, executes the query, and returns rows and column names.

  export async function queryReadOnly(
    sql: string,
    params?: QueryParams,
  ): Promise<{ rows: any[]; columns: string[] }> {
    if (!isReadOnlySelect(sql)) {
      throw new Error("Only read-only SELECT/WITH queries are allowed");
    }
    const pool = await getPool();
    const request = pool.request();
    if (params && typeof params === "object") {
      for (const [k, v] of Object.entries(params)) {
        request.input(k, mapJsToSqlType(v), v);
      }
    }
    const result = await request.query<any>(sql);
    const rows: any[] = (result.recordset as any[]) || [];
    const columns: string[] = rows[0] ? Object.keys(rows[0]) : [];
    return { rows, columns };
  }