SQLite MCP Server

Instructions

Implementation Reference

• src/index.ts:246-287 (handler)

  Executes the describe_table tool: checks database connection, runs PRAGMA table_info(?), formats columns with types, nullability, PK, defaults, and returns formatted schema text.

  private async describeTable(args: { table_name: string }): Promise<CallToolResult> {
    if (!this.db) {
      throw new Error("No database connected. Use connect_database first.");
    }
  
    try {
      const columns = this.db
        .prepare("PRAGMA table_info(?)")
        .all(args.table_name) as {
          cid: number;
          name: string;
          type: string;
          notnull: number;
          dflt_value: any;
          pk: number;
        }[];
  
      if (columns.length === 0) {
        throw new Error(`Table '${args.table_name}' not found`);
      }
  
      const schema = columns
        .map(col => {
          const nullable = col.notnull === 0 ? "NULL" : "NOT NULL";
          const pk = col.pk > 0 ? " PRIMARY KEY" : "";
          const defaultVal = col.dflt_value !== null ? ` DEFAULT ${col.dflt_value}` : "";
          return `  ${col.name} ${col.type} ${nullable}${pk}${defaultVal}`;
        })
        .join("\n");
  
      return {
        content: [
          {
            type: "text",
            text: `Table: ${args.table_name}\n\nSchema:\n${schema}`,
          } satisfies TextContent,
        ],
      };
    } catch (error) {
      throw new Error(`Failed to describe table: ${error instanceof Error ? error.message : String(error)}`);
    }
  }

• src/index.ts:86-99 (registration)

  Registers the describe_table tool in the ListTools response, including name, description, and input schema.

  {
    name: "describe_table",
    description: "Get the schema/structure of a specific table",
    inputSchema: {
      type: "object",
      properties: {
        table_name: {
          type: "string",
          description: "Name of the table to describe",
        },
      },
      required: ["table_name"],
    },
  },

• src/index.ts:89-98 (schema)

  Defines the input schema for describe_table: object with required 'table_name' string property.

  inputSchema: {
    type: "object",
    properties: {
      table_name: {
        type: "string",
        description: "Name of the table to describe",
      },
    },
    required: ["table_name"],
  },

• src/index.ts:168-170 (handler)

  Dispatches call_tool requests for describe_table to the describeTable method.

  case "describe_table":
    return await this.describeTable(args as { table_name: string });