run402

Instructions

Implementation Reference

• src/tools/get-schema.ts:10-91 (handler)

  Handler function that fetches and formats database schema information. It retrieves the project, makes an authenticated API request to get schema details, then formats the response as markdown tables showing tables, columns, types, constraints, and RLS policies.

  export async function handleGetSchema(args: {
    project_id: string;
  }): Promise<{ content: Array<{ type: "text"; text: string }>; isError?: boolean }> {
    const project = getProject(args.project_id);
    if (!project) return projectNotFound(args.project_id);
  
    const res = await apiRequest(`/admin/v1/projects/${args.project_id}/schema`, {
      method: "GET",
      headers: {
        Authorization: `Bearer ${project.service_key}`,
      },
    });
  
    if (!res.ok) return formatApiError(res, "fetching schema");
  
    const body = res.body as {
      schema: string;
      tables: Array<{
        name: string;
        columns: Array<{
          name: string;
          type: string;
          nullable: boolean;
          default_value: string | null;
        }>;
        constraints: Array<{
          name: string;
          type: string;
          definition: string;
        }>;
        rls_enabled: boolean;
        policies: Array<{
          name: string;
          command: string;
          using_expression: string | null;
          check_expression: string | null;
        }>;
      }>;
    };
  
    if (body.tables.length === 0) {
      return {
        content: [
          {
            type: "text",
            text: `## Schema: ${body.schema}\n\n_No tables found. Use \`run_sql\` to create tables._`,
          },
        ],
      };
    }
  
    const lines = [`## Schema: ${body.schema}`, ``];
  
    for (const table of body.tables) {
      lines.push(`### ${table.name}${table.rls_enabled ? " 🔒 RLS" : ""}`);
      lines.push(``);
      lines.push(`| Column | Type | Nullable | Default |`);
      lines.push(`|--------|------|----------|---------|`);
      for (const col of table.columns) {
        lines.push(
          `| ${col.name} | ${col.type} | ${col.nullable ? "YES" : "NO"} | ${col.default_value || "-"} |`,
        );
      }
  
      if (table.constraints.length > 0) {
        lines.push(``);
        lines.push(`**Constraints:** ${table.constraints.map((c) => `${c.type}(\`${c.name}\`)`).join(", ")}`);
      }
  
      if (table.policies.length > 0) {
        lines.push(``);
        lines.push(`**RLS Policies:**`);
        for (const p of table.policies) {
          lines.push(`- ${p.name} (${p.command})`);
        }
      }
  
      lines.push(``);
    }
  
    return { content: [{ type: "text", text: lines.join("\n") }] };
  }

• src/tools/get-schema.ts:6-8 (schema)

  Input schema definition using Zod that validates the tool accepts a single 'project_id' string parameter.

  export const getSchemaSchema = {
    project_id: z.string().describe("The project ID"),
  };

• src/index.ts:93-98 (registration)

  Registration of the 'get_schema' tool with the MCP server, providing the tool name, description, input schema, and handler function reference.

  server.tool(
    "get_schema",
    "Introspect the database schema — tables, columns, types, constraints, and RLS policies. Useful for understanding the database structure before writing queries.",
    getSchemaSchema,
    async (args) => handleGetSchema(args),
  );