15 tools with significant quality gaps. Tool names follow verb_noun pattern (sii_iniciar_sesion, sii_cerrar_sesion, etc.) but descriptions are minimal (10-50 chars, well below 194-char baseline). Input schemas present but sparse: most parameters lack type constraints, enums, or format specifications. No output schemas documented. Critical security issue: credentials (RUT, clave) exposed as parameters. No error handling guidance. Risk annotations present (WRITE, READ_ONLY, IRREVERSIBLE) but not integrated into descriptions. Composition is reasonable (single responsibility per tool), but parameter descriptions are generic ('RUT del contribuyente' repeated across tools without context on format/validation).

• Move RUT and clave to server-side secret injection (environment variables or vault). Remove from sii_iniciar_sesion parameters. Accept only a session_id or tenant_id that the server resolves internally.
• Expand all tool descriptions to 100-200 chars. Include WHEN to use (e.g., 'Call this after sii_iniciar_sesion to retrieve purchase records for a specific month'), WHAT it returns (e.g., 'Returns array of purchase documents with folio, date, amount, vendor RUT'), and any prerequisites.
• Document output schemas for all tools. Use JSON Schema format. E.g., sii_rcv_consultar returns {type: 'object', properties: {documentos: {type: 'array', items: {type: 'object', properties: {folio, fecha, monto, rut_proveedor}}}}}.
• Convert parameter descriptions to formal constraints: replace 'Período a consultar (YYYYMM)' with enum or pattern; replace 'compras o ventas' with enum: ['compras', 'ventas']. Add min/max for numeric params (e.g., año: 1900-2100).
• Add dry-run support to irreversible tools (sii_dte_emitir, sii_boleta_emitir, sii_rcv_escritura). Accept optional 'dry_run: boolean' parameter. Return simulated result without persisting. Include error recovery guidance: 'If emission fails, call sii_dte_verificar to check if document was partially created.'