# Duration add

`duration-add` · version 1.0.0 · Dates & times (UTC, ISO 8601) · free, no key needed

Sum mixed SI duration terms in nanoseconds and return the exact rational in a target unit.

**Use when you need to: duration add · add duration terms · sum mixed duration units.**

## Supported

- duration add
- add duration terms
- sum mixed duration units

## Not supported

- months
- years
- weeks
- leap seconds
- ISO-8601 duration strings
- average duration
- floats

## Behavior

- terms is a non-empty list of at most 32 {value, unit} duration amounts.
- Each value is a canonical integer string; unit is one of ns, us, ms, s, min, h, day.
- Terms are converted to nanoseconds with BigInt, summed, then expressed in the to unit as a reduced rational.
- day is exactly 86400 seconds; negative terms are allowed; leap seconds are not applied.
- Input integers and the reduced numerator and denominator may have at most 1000 digits excluding sign.

## Input

- `terms` (array of object, required): min items 1; max items 32
- `to` (one of "ns", "us", "ms", "s", "min", "h", "day", required)

## Output

- `numerator` (string, required): pattern `^(0|-?[1-9][0-9]*)$`
- `denominator` (string, required): pattern `^[1-9][0-9]*$`

## Limits

- max digits: 1000
- max terms: 32
- units: ["ns","us","ms","s","min","h","day"]

## Example

Request input:

```json
{
  "terms": [
    {
      "value": "1",
      "unit": "min"
    },
    {
      "value": "30",
      "unit": "s"
    }
  ],
  "to": "s"
}
```

Response:

```json
{
  "result": {
    "numerator": "90",
    "denominator": "1"
  }
}
```

## How to call it

### MCP

Connect `https://computefirst.net/mcp` ([setup](/docs#connect)), then call `execute` with:

```json
{
  "id": "duration-add",
  "version": "1.0.0",
  "input": {
    "terms": [
      {
        "value": "1",
        "unit": "min"
      },
      {
        "value": "30",
        "unit": "s"
      }
    ],
    "to": "s"
  }
}
```

### HTTP (no key)

```sh
curl -X POST https://computefirst.net/v1/tools/duration-add/versions/1.0.0/execute \
  -H "Content-Type: application/json" \
  -d '{"terms":[{"value":"1","unit":"min"},{"value":"30","unit":"s"}],"to":"s"}'
```

The machine-readable contract is at [/v1/tools/duration-add/versions/1.0.0](/v1/tools/duration-add/versions/1.0.0).

### CLI

```sh
node cli.mjs run duration-add 1.0.0 --input input.json --base-url https://computefirst.net
```

Get the client at [/clients/cli/](/clients/cli/).

## Related tools

- [Duration convert](/tools/duration-convert): Convert a canonical integer duration between nanosecond-based SI units as an exact rational.
- [Duration compare](/tools/duration-compare): Compare two SI duration amounts after converting both to nanoseconds.
- [ISO date add](/tools/iso-date-add): Add a signed whole-day delta to a strict YYYY-MM-DD calendar date.
- [ISO date add months](/tools/iso-date-add-months): Add a signed month count to a YYYY-MM-DD date, clamping the day to the target month.
- [ISO date add years](/tools/iso-date-add-years): Add a signed whole-year delta to a YYYY-MM-DD date, clamping the day if 29 February has no match.
- [ISO date business day add](/tools/iso-date-business-day-add): Add a signed count of business days to a date, skipping caller-supplied weekend weekdays and holidays.