Calcgrid

Convert units

convert_units

Read-onlyIdempotent

Use this when the user asks to convert a numeric value between units of the same physical quantity: length, mass, temperature, area, volume, speed, time, data, energy, pressure, power, angle, fuel economy, force, frequency, density or torque. Unit symbols and common names are accepted. Do not use this for currency, live exchange rates or cross-quantity conversions that require density. Returns the converted value, detected quantity, exact factor and a conversion table.

Input Schema

TableJSON Schema

Name	Required	Description
`value`	Yes	Value to convert.
`to_unit`	Yes	Target unit symbol or name, e.g. 'km'.
`from_unit`	Yes	Source unit symbol or name, e.g. 'mi', 'miles', '°C'.

Output Schema

TableJSON Schema

Name	Required	Description
`links`	No
`result`	Yes
`request`	Yes
`sources`	No
`success`	Yes
`version`	No
`freshness`	No
`timestamp`	Yes
`next_actions`	No
`service_version`	Yes	Deployed Calcgrid implementation version used for the result.

Schema Changelog

Changes observed during successful MCP inspections.

Changed2 schema fields changedSep 27, 2026

addedOutput schema / properties / service_version

Added value: +{
+  "description": "Deployed Calcgrid implementation version used for the result.",
+  "type": "string"
+}

changedOutput schema / required

Previous value: -[
-  "success",
-  "request",
-  "result",
-  "timestamp"
-]New value: +[
+  "success",
+  "service_version",
+  "request",
+  "result",
+  "timestamp"
+]

Changed15 schema fields changedSep 25, 2026

changedOutput schema / description

Previous value: -"Unified result envelope (see /docs/response-format.md)"New value: +"Deterministic calculation result with typed values, units, formula, sources and timestamp."

addedOutput schema / properties / next_actions / items
```
Added value: +{
+  "type": "object"
+}
```

addedOutput schema / properties / request / properties

Added value: +{
+  "calculator_id": {
+    "type": "string"
+  },
+  "inputs": {
+    "type": "object"
+  },
+  "tool": {
+    "type": "string"
+  }
+}

addedOutput schema / properties / result / properties / calculator_id
```
Added value: +{
+  "type": "string"
+}
```
addedOutput schema / properties / result / properties / calculator_name
```
Added value: +{
+  "type": "string"
+}
```

addedOutput schema / properties / result / properties / entity_type

Added value: +{
+  "const": "calculation",
+  "type": "string"
+}

addedOutput schema / properties / result / properties / status

Added value: +{
+  "const": "completed",
+  "type": "string"
+}

addedOutput schema / properties / result / properties / units / additionalProperties
```
Added value: +{
+  "type": "string"
+}
```
addedOutput schema / properties / result / properties / values / additionalProperties
```
Added value: +true
```

addedOutput schema / properties / result / required

Added value: +[
+  "entity_type",
+  "calculator_id",
+  "status",
+  "values",
+  "formula",
+  "summary"
+]

addedOutput schema / properties / sources / items
```
Added value: +{
+  "type": "object"
+}
```
addedOutput schema / properties / success / const
```
Added value: +true
```
addedOutput schema / properties / timestamp / format
```
Added value: +"date-time"
```
addedOutput schema / properties / version
```
Added value: +{
+  "type": "string"
+}
```

changedOutput schema / required

Previous value: -[
-  "success"
-]New value: +[
+  "success",
+  "request",
+  "result",
+  "timestamp"
+]

First observedSep 25, 2026

TDQS

A4.1/5.0

Behavior4/5

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

The annotations already convey readOnly, idempotent, and non-destructive behavior; the description adds that unit symbols and common names are accepted and that the result includes the converted value, detected quantity, exact factor, and a conversion table. There is no contradiction between the prose and the annotations.

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

Conciseness5/5

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

Three sentences, each earning its place: the trigger and scope, accepted unit forms, and exclusions plus return contents. It is front-loaded with the most important decision information and contains no filler.

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?

With all required parameters fully documented, rich annotations, an output schema present, and return behavior summarized in the description, an agent has everything needed to decide and invoke correctly. The described scope and exclusions also prevent common misuse.

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?

All three parameters have full descriptions in the input schema, so the baseline is 3. The tool description only reinforces that units can be symbols or names and does not add per-parameter format or edge-case details beyond the schema.

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

Purpose4/5

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

The description names a specific action and resource — converting a numeric value between units of the same physical quantity — and enumerates supported quantities explicitly. It does not, however, distinguish itself from the overlapping sibling convert_temperature, which also handles temperature conversions.

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?

It opens with a clear 'Use this when...' trigger and adds explicit exclusions for currency, live exchange rates, and density-requiring cross-quantity conversions. It stops short of naming any alternative tool for those cases, so the routing guidance is strong but not complete.

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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