MSSQL MCP Server

Instructions

Implementation Reference

• src/tools/DescribeTableTool.ts:17-34 (handler)

  The main handler function that executes the tool logic by querying the database's INFORMATION_SCHEMA.COLUMNS for the specified table's columns and types.

  async run(params: { tableName: string }) {
    try {
      const { tableName } = params;
      const request = new sql.Request();
      const query = `SELECT COLUMN_NAME as name, DATA_TYPE as type FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_NAME = @tableName`;
      request.input("tableName", sql.NVarChar, tableName);
      const result = await request.query(query);
      return {
        success: true,
        columns: result.recordset,
      };
    } catch (error) {
      return {
        success: false,
        message: `Failed to describe table: ${error}`,
      };
    }
  }

• src/tools/DescribeTableTool.ts:7-15 (schema)

  The tool's name, description, and input schema defining the required 'tableName' parameter.

  name = "describe_table";
  description = "Describes the schema (columns and types) of a specified MSSQL Database table.";
  inputSchema = {
    type: "object",
    properties: {
      tableName: { type: "string", description: "Name of the table to describe" },
    },
    required: ["tableName"],
  } as any;

• src/index.ts:109-113 (registration)

  Registration of the tool in the ListToolsRequestHandler, where describeTableTool is included in the list of available tools based on readonly mode.

  server.setRequestHandler(ListToolsRequestSchema, async () => ({
    tools: isReadOnly
      ? [listTableTool, readDataTool, describeTableTool] // todo: add searchDataTool to the list of tools available in readonly mode once implemented
      : [insertDataTool, readDataTool, describeTableTool, updateDataTool, createTableTool, createIndexTool, dropTableTool, listTableTool], // add all new tools here
  }));

• src/index.ts:141-149 (registration)

  Dispatch logic in CallToolRequestHandler that validates arguments and invokes the describeTableTool.run method.

  case describeTableTool.name:
    if (!args || typeof args.tableName !== "string") {
      return {
        content: [{ type: "text", text: `Missing or invalid 'tableName' argument for describe_table tool.` }],
        isError: true,
      };
    }
    result = await describeTableTool.run(args as { tableName: string });
    break;

• src/index.ts:90-90 (registration)

  Instantiation of the DescribeTableTool instance used throughout the server.

  const describeTableTool = new DescribeTableTool();