---
title: "Leer la ley fiscal"
description: "Lee un artículo de una ley fiscal mexicana oficial (o una regla de la RMF) como estaba en una fecha, lista las leyes disponibles o lista lo que cambió en ellas desde una fecha."
language: es-MX
canonical_url: "https://exac.mx/docs/mcp/tools/get_tax_law"
md_url: "https://exac.mx/docs/mcp/tools/get_tax_law.md"
---

# Leer la ley fiscal

Lee un artículo de una ley fiscal mexicana oficial (o una regla de la RMF) como estaba en una fecha, lista las leyes disponibles o lista lo que cambió en ellas desde una fecha.

Herramienta: `get_tax_law`

## Propósito

### Úsala cuando

Sabes qué artículo rige la duda, o necesitas ver qué cambió la ley recientemente.

### No la uses cuando

Aún no conoces el artículo; busca primero con search_tax_law.

| Detalle | Valor |
| --- | --- |
| Permisos | Ninguna |
| Efectos secundarios | Ninguno |
| Idempotencia | Idempotente |

## Esquema de entrada

```json
{
  "type": "object",
  "properties": {
    "input": {
      "oneOf": [
        {
          "type": "object",
          "properties": {
            "operation": {
              "const": "documents"
            }
          },
          "required": [
            "operation"
          ],
          "additionalProperties": false,
          "description": "The laws and regulations held, with their reform dates"
        },
        {
          "type": "object",
          "properties": {
            "operation": {
              "const": "article"
            },
            "law": {
              "$ref": "#/definitions/__schema2"
            },
            "article": {
              "type": "string",
              "minLength": 1,
              "maxLength": 40,
              "description": "Article as the law numbers it: 1o.-A, 29-A, 113-E, 3o-Bis, 17-H-Bis, Transitorios, Decreto-2019-12-09; an RMF rule: 2.7.1.34"
            },
            "asOf": {
              "description": "The date whose text is wanted (YYYY-MM-DD, Mexico City); defaults to today. Past dates return the version that bound then, from the corpus's history",
              "allOf": [
                {
                  "$ref": "#/definitions/__schema5"
                }
              ]
            },
            "offset": {
              "description": "Character to start the text at; use nextOffset",
              "allOf": [
                {
                  "type": "integer",
                  "minimum": 0,
                  "maximum": 9007199254740991
                }
              ]
            },
            "maxChars": {
              "description": "Characters of text to return; defaults to 30000. A long article is read in windows",
              "allOf": [
                {
                  "type": "integer",
                  "minimum": 1000,
                  "maximum": 60000
                }
              ]
            }
          },
          "required": [
            "operation",
            "law",
            "article"
          ],
          "additionalProperties": false,
          "description": "One article, its text in force on a date"
        },
        {
          "type": "object",
          "properties": {
            "operation": {
              "const": "changes"
            },
            "since": {
              "description": "Versions that took effect (validFrom) on or after this date",
              "allOf": [
                {
                  "$ref": "#/definitions/__schema5"
                }
              ]
            },
            "law": {
              "allOf": [
                {
                  "$ref": "#/definitions/__schema2"
                }
              ]
            },
            "kind": {
              "description": "article: the numbered articles (RMF: its rules); transitory: the law’s own transitory provisions; decree: the transitory articles of each reform decree, laws and regulations only (where commencement dates are)",
              "allOf": [
                {
                  "enum": [
                    "article",
                    "transitory",
                    "decree"
                  ]
                }
              ]
            },
            "cursor": {
              "description": "nextCursor of the previous page",
              "allOf": [
                {
                  "type": "string",
                  "minLength": 1
                }
              ]
            },
            "limit": {
              "description": "Results per page; defaults to 10",
              "allOf": [
                {
                  "type": "integer",
                  "minimum": 1,
                  "maximum": 25
                }
              ]
            }
          },
          "required": [
            "operation",
            "since"
          ],
          "additionalProperties": false,
          "description": "Versions by their validFrom, newest first, without text"
        }
      ]
    }
  },
  "required": [
    "input"
  ],
  "$schema": "http://json-schema.org/draft-07/schema#",
  "additionalProperties": false,
  "definitions": {
    "__schema2": {
      "enum": [
        "LIVA",
        "LISR",
        "CFF",
        "LIEPS",
        "LSS",
        "LFT",
        "LDVUMA",
        "RLIVA",
        "RLISR",
        "RCFF",
        "RLIEPS",
        "RMF"
      ],
      "description": "A law, regulation or the RMF: LIVA, LISR, CFF, LIEPS, LSS, LFT, LDVUMA, RLIVA, RLISR, RCFF, RLIEPS, RMF"
    },
    "__schema5": {
      "type": "string",
      "format": "date",
      "pattern": "^(?:(?:\\d\\d[2468][048]|\\d\\d[13579][26]|\\d\\d0[48]|[02468][048]00|[13579][26]00)-02-29|\\d{4}-(?:(?:0[13578]|1[02])-(?:0[1-9]|[12]\\d|3[01])|(?:0[469]|11)-(?:0[1-9]|[12]\\d|30)|(?:02)-(?:0[1-9]|1\\d|2[0-8])))$"
    }
  }
}
```

## Esquema de salida

```json
{
  "type": "object",
  "properties": {
    "data": {
      "anyOf": [
        {
          "type": "object",
          "properties": {
            "documents": {
              "type": "array",
              "items": {
                "type": "object",
                "properties": {
                  "law": {
                    "$ref": "#/definitions/__schema0"
                  },
                  "name": {
                    "type": "string"
                  },
                  "kind": {
                    "enum": [
                      "law",
                      "regulation",
                      "resolution"
                    ]
                  },
                  "edition": {
                    "allOf": [
                      {
                        "type": "string"
                      }
                    ]
                  },
                  "reformedOn": {
                    "anyOf": [
                      {
                        "$ref": "#/definitions/__schema2"
                      },
                      {
                        "type": "null"
                      }
                    ]
                  },
                  "lastCheckedAt": {
                    "anyOf": [
                      {
                        "$ref": "#/definitions/__schema3"
                      },
                      {
                        "type": "null"
                      }
                    ]
                  },
                  "stale": {
                    "type": "array",
                    "items": {
                      "type": "object",
                      "properties": {
                        "kind": {
                          "$ref": "#/definitions/__schema5"
                        },
                        "since": {
                          "$ref": "#/definitions/__schema3"
                        },
                        "note": {
                          "$ref": "#/definitions/__schema6"
                        }
                      },
                      "required": [
                        "kind",
                        "since"
                      ],
                      "additionalProperties": false
                    }
                  }
                },
                "required": [
                  "law",
                  "name",
                  "kind",
                  "reformedOn",
                  "lastCheckedAt",
                  "stale"
                ],
                "additionalProperties": false
              }
            },
            "notice": {
              "type": "string"
            }
          },
          "required": [
            "documents",
            "notice"
          ],
          "additionalProperties": false
        },
        {
          "type": "object",
          "properties": {
            "article": {
              "type": "object",
              "properties": {
                "law": {
                  "$ref": "#/definitions/__schema0"
                },
                "article": {
                  "$ref": "#/definitions/__schema8"
                },
                "headings": {
                  "$ref": "#/definitions/__schema9"
                },
                "validFrom": {
                  "$ref": "#/definitions/__schema2"
                },
                "validTo": {
                  "$ref": "#/definitions/__schema11"
                },
                "citationUrl": {
                  "$ref": "#/definitions/__schema12"
                },
                "text": {
                  "type": "string"
                },
                "textLength": {
                  "type": "number"
                },
                "offset": {
                  "type": "number"
                },
                "nextOffset": {
                  "anyOf": [
                    {
                      "type": "number"
                    },
                    {
                      "type": "null"
                    }
                  ]
                }
              },
              "required": [
                "law",
                "article",
                "headings",
                "validFrom",
                "validTo",
                "citationUrl",
                "text",
                "textLength",
                "offset",
                "nextOffset"
              ],
              "additionalProperties": false
            },
            "previousVersion": {
              "anyOf": [
                {
                  "$ref": "#/definitions/__schema14"
                },
                {
                  "type": "null"
                }
              ]
            },
            "nextVersion": {
              "anyOf": [
                {
                  "$ref": "#/definitions/__schema14"
                },
                {
                  "type": "null"
                }
              ]
            },
            "stale": {
              "$ref": "#/definitions/__schema15"
            },
            "notice": {
              "type": "string"
            }
          },
          "required": [
            "article",
            "previousVersion",
            "nextVersion",
            "stale",
            "notice"
          ],
          "additionalProperties": false
        },
        {
          "type": "object",
          "properties": {
            "changes": {
              "type": "array",
              "items": {
                "type": "object",
                "properties": {
                  "law": {
                    "$ref": "#/definitions/__schema0"
                  },
                  "article": {
                    "$ref": "#/definitions/__schema8"
                  },
                  "headings": {
                    "$ref": "#/definitions/__schema9"
                  },
                  "validFrom": {
                    "$ref": "#/definitions/__schema2"
                  },
                  "validTo": {
                    "$ref": "#/definitions/__schema11"
                  },
                  "citationUrl": {
                    "$ref": "#/definitions/__schema12"
                  }
                },
                "required": [
                  "law",
                  "article",
                  "headings",
                  "validFrom",
                  "validTo",
                  "citationUrl"
                ],
                "additionalProperties": false
              }
            },
            "nextCursor": {
              "anyOf": [
                {
                  "type": "string"
                },
                {
                  "type": "null"
                }
              ]
            },
            "stale": {
              "$ref": "#/definitions/__schema15"
            },
            "notice": {
              "type": "string"
            }
          },
          "required": [
            "changes",
            "nextCursor",
            "stale",
            "notice"
          ],
          "additionalProperties": false
        }
      ]
    },
    "error": {
      "$schema": "http://json-schema.org/draft-07/schema#",
      "type": "object",
      "properties": {
        "code": {
          "enum": [
            "validation_error",
            "unauthenticated",
            "forbidden",
            "payment_required",
            "not_found",
            "method_not_allowed",
            "conflict",
            "idempotency_conflict",
            "operation_in_progress",
            "recovery_required",
            "migration_required",
            "rate_limited",
            "provider_unavailable",
            "internal"
          ]
        },
        "message": {
          "type": "string"
        },
        "details": {
          "type": "object",
          "properties": {
            "document": {
              "type": "object",
              "properties": {
                "documentRef": {
                  "type": "string",
                  "pattern": "^(invoice|withholding|sales_receipt|declaration|tax_compliance_opinion|sales_receipt_refund):.+$"
                },
                "editable": {
                  "type": "boolean"
                }
              },
              "required": [
                "documentRef",
                "editable"
              ],
              "additionalProperties": false
            },
            "issues": {
              "type": "array",
              "items": {
                "type": "object",
                "properties": {
                  "path": {
                    "type": "array",
                    "items": {
                      "anyOf": [
                        {
                          "type": "string"
                        },
                        {
                          "type": "number"
                        }
                      ]
                    }
                  },
                  "message": {
                    "type": "string"
                  },
                  "code": {
                    "type": "string"
                  }
                },
                "required": [
                  "path",
                  "message"
                ],
                "additionalProperties": false
              }
            },
            "retryable": {
              "type": "boolean"
            },
            "retryAfterSeconds": {
              "type": "integer",
              "exclusiveMinimum": 0,
              "maximum": 9007199254740991
            },
            "reason": {
              "type": "string"
            },
            "balanceMinor": {
              "type": "integer",
              "minimum": 0,
              "maximum": 9007199254740991
            },
            "topUpUrl": {
              "type": "string"
            }
          },
          "additionalProperties": false
        }
      },
      "required": [
        "code",
        "message"
      ],
      "additionalProperties": false
    }
  },
  "$schema": "http://json-schema.org/draft-07/schema#",
  "additionalProperties": false,
  "definitions": {
    "__schema0": {
      "enum": [
        "LIVA",
        "LISR",
        "CFF",
        "LIEPS",
        "LSS",
        "LFT",
        "LDVUMA",
        "RLIVA",
        "RLISR",
        "RCFF",
        "RLIEPS",
        "RMF"
      ]
    },
    "__schema2": {
      "type": "string",
      "format": "date"
    },
    "__schema3": {
      "type": "string",
      "format": "date-time"
    },
    "__schema5": {
      "enum": [
        "failing",
        "lagging"
      ]
    },
    "__schema6": {
      "allOf": [
        {
          "type": "string"
        }
      ]
    },
    "__schema8": {
      "type": "string"
    },
    "__schema9": {
      "type": "array",
      "items": {
        "type": "string"
      }
    },
    "__schema11": {
      "anyOf": [
        {
          "$ref": "#/definitions/__schema2"
        },
        {
          "type": "null"
        }
      ]
    },
    "__schema12": {
      "type": "string"
    },
    "__schema14": {
      "type": "object",
      "properties": {
        "validFrom": {
          "$ref": "#/definitions/__schema2"
        },
        "validTo": {
          "anyOf": [
            {
              "$ref": "#/definitions/__schema2"
            },
            {
              "type": "null"
            }
          ]
        }
      },
      "required": [
        "validFrom",
        "validTo"
      ],
      "additionalProperties": false
    },
    "__schema15": {
      "type": "array",
      "items": {
        "type": "object",
        "properties": {
          "law": {
            "$ref": "#/definitions/__schema0"
          },
          "kind": {
            "$ref": "#/definitions/__schema5"
          },
          "since": {
            "$ref": "#/definitions/__schema3"
          },
          "note": {
            "$ref": "#/definitions/__schema6"
          }
        },
        "required": [
          "law",
          "kind",
          "since"
        ],
        "additionalProperties": false
      }
    }
  },
  "oneOf": [
    {
      "required": [
        "data"
      ]
    },
    {
      "required": [
        "error"
      ]
    }
  ]
}
```

## Herramientas relacionadas

- [`search_tax_law`](/docs/mcp/tools/search_tax_law.md) — **Buscar en la ley fiscal**: Busca en el texto oficial de la ley fiscal y laboral mexicana (LISR, LIVA, CFF, LIEPS, LSS, LFT y sus reglamentos, consolidados por la Cámara de Diputados, y la RMF del SAT) y devuelve los pasajes que coinciden, con su cita. Devuelve fuentes, no respuestas: lee el artículo de un pasaje con get_tax_law.

- [`get_tax_rules`](/docs/mcp/tools/get_tax_rules.md) — **Leer parámetros fiscales**: Lee los parámetros fiscales con que calcula Exac (tasas de IVA, tarifas de ISR, UMA, salarios mínimos, cuotas del IMSS, reglas de retención) y sus valores en una fecha, con la publicación que establece cada uno.

## Flujo relacionado

[Consulta los flujos canónicos en Inicio rápido](/docs.md)

Documentación completa: https://exac.mx/docs.md
Índice para agentes: https://exac.mx/docs/llms.txt