FreightUtils MCP Server

Unit Converter

unit_converter

Read-onlyIdempotent

Convert freight and logistics units: weight (kg, lbs, oz, tonnes, short_tons, long_tons), volume (cbm, cuft, cuin, litres, gal_us, gal_uk), length (cm, inches, m, feet, mm), plus two freight-specific targets valid only FROM cbm — chargeable_kg (air volumetric weight at the IATA 6,000 divisor: m³ x 1,000,000 / 6000) and freight_tonnes (sea W/M, 1 CBM = 1 freight tonne).

Behavior: deterministic, on the exact legal factors (1 lb = 0.45359237 kg, 1 in = 2.54 cm); the response names both units and states the formula used. Cross-dimension conversions (e.g. kg to litres), a negative value and freight targets from a non-cbm source are refused with the accepted units listed by category. Note: short ton (US) = 2,000 lb, long ton (UK) = 2,240 lb, metric tonne = 2,204.6 lb. Rate-limited: a limit error carries reset_at, the UTC time the allowance resets.

Returns: input {value, unit, name}, result {value, unit, name}, formula and note under result, plus confidence, _source and citation (the FreightUtils v1 response envelope).

Related: cbm_calculator (dimensions to volume first), chargeable_weight_calculator (proper air billing weight with pieces and a custom divisor).

Input Schema

Name	Required	Description
`to`	Yes	Target unit — any source unit, plus the freight targets chargeable_kg and freight_tonnes (only valid from cbm)
`from`	Yes	Source unit — weight (kg, lbs, oz, tonnes, short_tons, long_tons), volume (cbm, cuft, cuin, litres, gal_us, gal_uk) or length (cm, inches, m, feet, mm)
`value`	Yes	Value to convert

Output Schema

Name	Required	Description	Default
`ok`	Yes
`_meta`	No
`as_of`	No
`result`	Yes
`status`	No
`_source`	Yes
`edition`	No
`citation`	Yes
`validity`	No
`warnings`	No
`confidence`	Yes
`missing_inputs`	No
`blocking_errors`	No
`envelope_version`	Yes
`normalized_input`	No

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedNov 6, 2026

addedOutput schema / properties / _meta / properties / upstream

Added value: +{
+  "additionalProperties": {},
+  "properties": {
+    "datasets": {
+      "additionalProperties": {
+        "additionalProperties": {},
+        "properties": {
+          "kind": {
+            "anyOf": [
+              {
+                "enum": [
+                  "watched",
+                  "checksum-only",
+                  "manual"
+                ],
+                "type": "string"
+              },
+              {
+                "type": "null"
+              }
+            ]
+          },
+          "last_success": {
+            "type": [
+              "string",
+              "null"
+            ]
+          },
+          "reason": {
+            "type": "string"
+          },
+          "stale": {
+            "type": "boolean"
+          },
+          "state": {
+            "enum": [
+              "in_step",
+              "changed_upstream",
+              "schema_drift",
+              "unreachable",
+              "window_missed",
+              "unknown"
+            ],
+            "type": "string"
+          },
+          "window_days": {
+            "type": [
+              "number",
+              "null"
+            ]
+          }
+        },
+        "required": [
+          "state",
+          "kind",
+          "last_success",
+          "window_days",
+          "stale"
+        ],
+        "type": "object"
+      },
+      "propertyNames": {
+        "type": "string"
+      },
+      "type": "object"
+    },
+    "stale": {
+      "type": "boolean"
+    },
+    "state": {
+      "enum": [
+        "in_step",
+        "changed_upstream",
+        "schema_drift",
+        "unreachable",
+        "window_missed",
+        "unknown"
+      ],
+      "type": "string"
+    },
+    "state_read_at": {
+      "type": [
+        "string",
+        "null"
+      ]
+    }
+  },
+  "required": [
+    "state",
+    "stale",
+    "state_read_at",
+    "datasets"
+  ],
+  "type": "object"
+}

Changed1 schema field changedNov 6, 2026

addedOutput schema / properties / _meta / properties / ids

Added value: +{
+  "additionalProperties": false,
+  "properties": {
+    "pattern": {
+      "type": "string"
+    },
+    "scheme": {
+      "maximum": 9007199254740991,
+      "minimum": -9007199254740991,
+      "type": "integer"
+    }
+  },
+  "required": [
+    "scheme",
+    "pattern"
+  ],
+  "type": "object"
+}

Changed2 schema fields changedNov 4, 2026
- removedOutput schema / properties / _meta / properties / receipt / properties / reason / const
```
Removed value: -"key_required"
```
- addedOutput schema / properties / _meta / properties / receipt / properties / reason / enum
```
Added value: +[
+  "key_required",
+  "quota"
+]
```

Changed1 schema field changedOct 30, 2026

addedOutput schema / properties / _meta / properties / receipt

Added value: +{
+  "additionalProperties": {},
+  "properties": {
+    "created_at": {
+      "type": "string"
+    },
+    "dataset_version": {
+      "additionalProperties": {
+        "type": "string"
+      },
+      "propertyNames": {
+        "type": "string"
+      },
+      "type": "object"
+    },
+    "engine_version": {
+      "type": "string"
+    },
+    "inputs": {},
+    "reason": {
+      "const": "key_required",
+      "type": "string"
+    },
+    "receipt_hash": {
+      "type": "string"
+    },
+    "result": {
+      "additionalProperties": {},
+      "propertyNames": {
+        "type": "string"
+      },
+      "type": "object"
+    },
+    "schema_version": {
+      "type": "string"
+    },
+    "stored": {
+      "const": false,
+      "type": "boolean"
+    },
+    "tool": {
+      "type": "string"
+    }
+  },
+  "required": [
+    "stored",
+    "reason",
+    "schema_version",
+    "receipt_hash",
+    "created_at",
+    "tool",
+    "inputs",
+    "dataset_version",
+    "engine_version",
+    "result"
+  ],
+  "type": "object"
+}

Changed1 schema field changedOct 29, 2026
- addedOutput schema / properties / _meta / properties / edition_basis
```
Added value: +{
+  "type": "string"
+}
```

Changed1 schema field changedOct 29, 2026

addedOutput schema / properties / _meta

Added value: +{
+  "additionalProperties": {},
+  "properties": {
+    "check_id": {
+      "type": "string"
+    },
+    "receipt_url": {
+      "type": "string"
+    }
+  },
+  "type": "object"
+}

Changed5 schema fields changedOct 29, 2026

addedOutput schema / properties / as_of

Added value: +{
+  "pattern": "^\\d{4}-\\d{2}-\\d{2}$",
+  "type": "string"
+}

addedOutput schema / properties / edition

Added value: +{
+  "anyOf": [
+    {
+      "additionalProperties": false,
+      "properties": {
+        "applies_from": {
+          "type": [
+            "string",
+            "null"
+          ]
+        },
+        "may_apply_until": {
+          "type": [
+            "string",
+            "null"
+          ]
+        },
+        "name": {
+          "type": "string"
+        }
+      },
+      "required": [
+        "name",
+        "applies_from",
+        "may_apply_until"
+      ],
+      "type": "object"
+    },
+    {
+      "type": "null"
+    }
+  ]
+}

changedOutput schema / properties / envelope_version / enum

Previous value: -[
-  "1",
-  "1.1"
-]New value: +[
+  "1",
+  "1.1",
+  "1.2"
+]

addedOutput schema / properties / missing_inputs

Added value: +{
+  "items": {
+    "type": "string"
+  },
+  "type": "array"
+}

addedOutput schema / properties / status

Added value: +{
+  "enum": [
+    "ok",
+    "partial",
+    "not_found",
+    "unsupported",
+    "ambiguous"
+  ],
+  "type": "string"
+}

Changed2 schema fields changedOct 28, 2026
- removedOutput schema / properties / validity / properties / effective_to / anyOf
```
Removed value: -[
-  {
-    "type": "string"
-  },
-  {
-    "type": "null"
-  }
-]
```
- addedOutput schema / properties / validity / properties / effective_to / type
```
Added value: +[
+  "string",
+  "null"
+]
```
Changed1 schema field changedOct 8, 2026
- addedInput schema / additionalProperties
```
Added value: +false
```
Changed5 schema fields changedAug 11, 2026
- addedOutput schema / properties / _source / properties / authority_current_edition
```
Added value: +{
+  "type": "string"
+}
```
- addedOutput schema / properties / _source / properties / checked_at
```
Added value: +{
+  "type": "string"
+}
```
- addedOutput schema / properties / _source / properties / dataset_edition
```
Added value: +{
+  "type": "string"
+}
```
- removedOutput schema / properties / envelope_version / const
```
Removed value: -"1"
```
- addedOutput schema / properties / envelope_version / enum
```
Added value: +[
+  "1",
+  "1.1"
+]
```

Changed1 schema field changedJul 9, 2026

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "additionalProperties": false,
+  "properties": {
+    "_source": {
+      "additionalProperties": false,
+      "properties": {
+        "checked": {
+          "type": "string"
+        },
+        "name": {
+          "type": "string"
+        },
+        "provenance_status": {
+          "enum": [
+            "verified",
+            "pending-verification",
+            "computed",
+            "live"
+          ],
+          "type": "string"
+        },
+        "source_url": {
+          "type": "string"
+        }
+      },
+      "required": [
+        "name",
+        "checked",
+        "provenance_status"
+      ],
+      "type": "object"
+    },
+    "blocking_errors": {
+      "items": {
+        "additionalProperties": false,
+        "properties": {
+          "code": {
+            "type": "string"
+          },
+          "message": {
+            "type": "string"
+          },
+          "recovery": {
+            "additionalProperties": false,
+            "properties": {
+              "action": {
+                "type": "string"
+              },
+              "params": {
+                "additionalProperties": {},
+                "propertyNames": {
+                  "type": "string"
+                },
+                "type": "object"
+              },
+              "tool": {
+                "type": "string"
+              }
+            },
+            "required": [
+              "action"
+            ],
+            "type": "object"
+          }
+        },
+        "required": [
+          "code",
+          "message",
+          "recovery"
+        ],
+        "type": "object"
+      },
+      "type": "array"
+    },
+    "citation": {
+      "additionalProperties": false,
+      "properties": {
+        "qualifier": {
+          "type": "string"
+        },
+        "text": {
+          "type": "string"
+        }
+      },
+      "required": [
+        "text"
+      ],
+      "type": "object"
+    },
+    "confidence": {
+      "additionalProperties": false,
+      "properties": {
+        "basis": {
+          "enum": [
+            "deterministic",
+            "provenance",
+            "match_quality",
+            "freshness"
+          ],
+          "type": "string"
+        },
+        "level": {
+          "enum": [
+            "high",
+            "medium",
+            "low"
+          ],
+          "type": "string"
+        },
+        "score": {
+          "maximum": 1,
+          "minimum": 0,
+          "type": "number"
+        }
+      },
+      "required": [
+        "level",
+        "basis"
+      ],
+      "type": "object"
+    },
+    "envelope_version": {
+      "const": "1",
+      "type": "string"
+    },
+    "normalized_input": {
+      "additionalProperties": {},
+      "propertyNames": {
+        "type": "string"
+      },
+      "type": "object"
+    },
+    "ok": {
+      "type": "boolean"
+    },
+    "result": {
+      "additionalProperties": {},
+      "propertyNames": {
+        "type": "string"
+      },
+      "type": "object"
+    },
+    "validity": {
+      "additionalProperties": false,
+      "properties": {
+        "as_of": {
+          "type": "string"
+        },
+        "effective_from": {
+          "type": "string"
+        },
+        "effective_to": {
+          "anyOf": [
+            {
+              "type": "string"
+            },
+            {
+              "type": "null"
+            }
+          ]
+        }
+      },
+      "required": [
+        "as_of"
+      ],
+      "type": "object"
+    },
+    "warnings": {
+      "items": {
+        "additionalProperties": false,
+        "properties": {
+          "code": {
+            "type": "string"
+          },
+          "details": {
+            "additionalProperties": {},
+            "propertyNames": {
+              "type": "string"
+            },
+            "type": "object"
+          },
+          "message": {
+            "type": "string"
+          }
+        },
+        "required": [
+          "code",
+          "message"
+        ],
+        "type": "object"
+      },
+      "type": "array"
+    }
+  },
+  "required": [
+    "envelope_version",
+    "ok",
+    "result",
+    "confidence",
+    "_source",
+    "citation"
+  ],
+  "type": "object"
+}

Changed4 schema fields changedJun 19, 2026

changedInput schema / properties / from / description

Previous value: -"Source unit"New value: +"Source unit — weight (kg, lbs, oz, tonnes, short_tons, long_tons), volume (cbm, cuft, cuin, litres, gal_us, gal_uk) or length (cm, inches, m, feet, mm)"

addedInput schema / properties / from / enum

Added value: +[
+  "kg",
+  "lbs",
+  "oz",
+  "tonnes",
+  "short_tons",
+  "long_tons",
+  "cbm",
+  "cuft",
+  "cuin",
+  "litres",
+  "gal_us",
+  "gal_uk",
+  "cm",
+  "inches",
+  "m",
+  "feet",
+  "mm"
+]

changedInput schema / properties / to / description

Previous value: -"Target unit"New value: +"Target unit — any source unit, plus the freight targets chargeable_kg and freight_tonnes (only valid from cbm)"

addedInput schema / properties / to / enum

Added value: +[
+  "kg",
+  "lbs",
+  "oz",
+  "tonnes",
+  "short_tons",
+  "long_tons",
+  "cbm",
+  "cuft",
+  "cuin",
+  "litres",
+  "gal_us",
+  "gal_uk",
+  "cm",
+  "inches",
+  "m",
+  "feet",
+  "mm",
+  "chargeable_kg",
+  "freight_tonnes"
+]

First observedApr 23, 2026

TDQS

A4.6/5.0

Behavior4/5

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

Annotations already declare readOnly, idempotent, non-destructive, closed-world, so the safety profile is covered; the description still adds real value by promising deterministic exact legal factors, describing refusal behavior with accepted units listed by category, and disclosing that rate-limit errors carry reset_at. The response-envelope sentence duplicates what the output schema likely already exposes, which keeps it off a 5.

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?

Purpose is front-loaded and the Behavior/Returns/Related blocks make it scannable; nearly every sentence carries operational information. The listing of the returned envelope fields (confidence, _source, citation) is the one segment that spends words on something an output schema already conveys.

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?

For a three-parameter converter with an output schema, annotation coverage, and two enum-constrained fields, the description covers everything an agent needs: legal factors, dimension restrictions, error and refusal semantics, and sibling routing. Nothing material is left for the agent to guess.

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

Parameters4/5

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

Schema coverage is 100% and the enums are self-documenting, so the schema carries the baseline. The description still adds meaning the schema cannot: the IATA 6,000 divisor formula for chargeable_kg, the 1 CBM = 1 freight tonne W/M rule, the short/long/metric ton distinctions, and the source restriction on the two freight targets.

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?

The description opens with a specific verb and resource ("Convert freight and logistics units") and enumerates the exact unit families and members it supports. The closing "Related:" line names cbm_calculator and chargeable_weight_calculator, so an agent can separate this general converter from the specialized calculators without opening a schema.

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

Usage Guidelines5/5

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

It states the preconditions explicitly: chargeable_kg and freight_tonnes are valid only FROM cbm, and cross-dimension conversions are refused. It also routes the agent to the right alternative in the two cases where a sibling is better — dimensions-to-volume via cbm_calculator, and proper air billing weight with pieces/custom divisor via chargeable_weight_calculator.

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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