Nettomaandinkomen

Fiscale kerncijfers opvragen (NL 2026)

nmi_fiscale_regels

Read-onlyIdempotent

Geeft de kerncijfers waarmee de NMI-rekenkern werkt: belastingschijven, heffingskortingen, maximumdagloon, WW- en WIA-percentages, minimumloon, vakantiegeld en de 30%-regeling. Gebruik om tarieven op te halen of te controleren in plaats van ze uit het geheugen te noemen. Niet gebruiken voor een persoonlijke berekening (gebruik de rekentool voor die vraag). Read-only, geen invoer nodig behalve eventueel het jaar.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`fiscalYear`	No	Rekenjaar. Beschikbaar: 2026. Standaard 2026.

Output Schema

TableJSON Schema

Name	Required	Description	Default
`regels`	Yes	Kerncijfers van de NMI-rekenkern; gebruik deze in plaats van tarieven uit het geheugen.

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedSep 28, 2026

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "additionalProperties": false,
+  "properties": {
+    "regels": {
+      "additionalProperties": false,
+      "description": "Kerncijfers van de NMI-rekenkern; gebruik deze in plaats van tarieven uit het geheugen.",
+      "properties": {
+        "belastingschijven": {
+          "items": {
+            "additionalProperties": false,
+            "properties": {
+              "label": {
+                "type": "string"
+              },
+              "tarief": {
+                "description": "Tarief als fractie (0,358 = 35,8%).",
+                "type": "number"
+              },
+              "tot_en_met": {
+                "description": "Bovengrens van de schijf in euro.",
+                "type": "number"
+              }
+            },
+            "required": [
+              "label",
+              "tot_en_met",
+              "tarief"
+            ],
+            "type": "object"
+          },
+          "type": "array"
+        },
+        "bron": {
+          "type": "string"
+        },
+        "documentatie": {
+          "description": "Link naar nettomaandinkomen.nl.",
+          "type": "string"
+        },
+        "fiscal_year": {
+          "description": "Rekenjaar van de kerncijfers.",
+          "type": "number"
+        },
+        "heffingskortingen": {
+          "additionalProperties": false,
+          "properties": {
+            "algemene_heffingskorting": {
+              "type": "number"
+            },
+            "algemene_heffingskorting_aow": {
+              "type": "number"
+            },
+            "arbeidskorting_segmenten": {
+              "additionalProperties": false,
+              "description": "Opbouw- en afbouwsegmenten van de arbeidskorting.",
+              "properties": {
+                "max": {
+                  "description": "Maximale arbeidskorting in euro.",
+                  "type": "number"
+                },
+                "segments": {
+                  "items": {
+                    "additionalProperties": false,
+                    "properties": {
+                      "base": {
+                        "description": "Basisbedrag aan het begin van het segment.",
+                        "type": "number"
+                      },
+                      "limit": {
+                        "description": "Bovengrens van het segment in euro.",
+                        "type": "number"
+                      },
+                      "rate": {
+                        "description": "Opbouw (positief) of afbouw (negatief) als fractie.",
+                        "type": "number"
+                      },
+                      "threshold": {
+                        "description": "Ondergrens van het segment in euro.",
+                        "type": "number"
+                      }
+                    },
+                    "required": [
+                      "limit",
+                      "base",
+                      "rate",
+                      "threshold"
+                    ],
+                    "type": "object"
+                  },
+                  "type": "array"
+                }
+              },
+              "required": [
+                "max",
+                "segments"
+              ],
+              "type": "object"
+            }
+          },
+          "required": [
+            "algemene_heffingskorting",
+            "algemene_heffingskorting_aow",
+            "arbeidskorting_segmenten"
+          ],
+          "type": "object"
+        },
+        "minimumloon": {
+          "additionalProperties": false,
+          "properties": {
+            "bruto_maand_referentie": {
+              "type": "number"
+            },
+            "minimumuurloon": {
+              "type": "number"
+            }
+          },
+          "required": [
+            "bruto_maand_referentie",
+            "minimumuurloon"
+          ],
+          "type": "object"
+        },
+        "toelichting": {
+          "type": "string"
+        },
+        "uwv": {
+          "additionalProperties": false,
+          "properties": {
+            "gemiddelde_dagen_per_maand": {
+              "type": "number"
+            },
+            "maximumdagloon_actief": {
+              "type": "number"
+            },
+            "werkdagen_per_jaar": {
+              "type": "number"
+            },
+            "wga_percentage_daarna": {
+              "type": "number"
+            },
+            "wga_percentage_eerste_twee_maanden": {
+              "type": "number"
+            },
+            "wia_iva_percentage": {
+              "type": "number"
+            },
+            "ww_percentage_daarna": {
+              "type": "number"
+            },
+            "ww_percentage_eerste_twee_maanden": {
+              "type": "number"
+            }
+          },
+          "required": [
+            "maximumdagloon_actief",
+            "werkdagen_per_jaar",
+            "gemiddelde_dagen_per_maand",
+            "ww_percentage_eerste_twee_maanden",
+            "ww_percentage_daarna",
+            "wia_iva_percentage",
+            "wga_percentage_eerste_twee_maanden",
+            "wga_percentage_daarna"
+          ],
+          "type": "object"
+        },
+        "vakantiegeld": {
+          "description": "Wettelijk minimum als fractie (0,08 = 8%).",
+          "type": "number"
+        }
+      },
+      "required": [
+        "fiscal_year",
+        "belastingschijven",
+        "heffingskortingen",
+        "uwv",
+        "minimumloon",
+        "vakantiegeld",
+        "bron",
+        "toelichting",
+        "documentatie"
+      ],
+      "type": "object"
+    }
+  },
+  "required": [
+    "regels"
+  ],
+  "type": "object"
+}

AddedSep 26, 2026

TDQS

A4/5.0

Behavior3/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnlyHint=true, idempotentHint=true and openWorldHint=false, so the 'Read-only' sentence largely repeats structured data. The added value is the note that no input is required apart from the optional year, but nothing is said about caching, versioning of the figures, or coverage of non-2026 years.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Front-loaded with the resource content, then usage, then the exclusion and the read-only note. The enumeration of fiscal items is long but functional for retrieval; every sentence carries information, with only minor redundancy in restating the read-only annotation.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

An output schema exists, so return values need no explanation. For a zero-required-parameter read-only lookup, the description supplies purpose, contents, usage, exclusion and the optional-year caveat — nothing an agent needs in order to call it correctly is missing.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100% and the single fiscalYear parameter is already documented in the schema (available: 2026, default 2026). The description only echoes this with 'eventueel het jaar', adding no format or edge-case detail beyond the schema. Baseline 3 applies.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource ('Geeft de kerncijfers waarmee de NMI-rekenkern werkt') and enumerates the exact contents (belastingschijven, heffingskortingen, maximumdagloon, WW/WIA, minimumloon, vakantiegeld, 30%-regeling). It also explicitly distinguishes itself from the calculation siblings by declaring what it is not for.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Gives clear when-to-use ('Gebruik om tarieven op te halen of te controleren in plaats van ze uit het geheugen te noemen') and an explicit when-not ('Niet gebruiken voor een persoonlijke berekening'). The alternative is referenced only generically as 'de rekentool' rather than by one of the concrete sibling names such as nmi_bruto_netto or nmi_netto_inkomen_volledig, so routing is slightly less precise than it could be.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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