MCP tools

Record numbers

record_readings sends numbers for metrics already defined, such as a day's revenue or signups.

record_readings

record_readings records numbers for metrics that are already defined: a day's revenue, signups, or anything else a decision is measured by.

Sending the same reading again is safe.
To send numbers from a script instead of an AI tool, see Send numbers to hosted ZeroWidth.
A metric that isn't defined is refused, never created by record_readings. Define it first with define_metric: give a name and say which way is good, higher or lower. A name that already exists is left as it is. An admin can also define metrics in the console; self-hosted, metrics are defined from files or the command line. Metrics
On hosted ZeroWidth, only admins' agents get define_metric and record_readings.
If any reading in a call is wrong, none of the readings are kept.

Input	What to send
`readings`	A list of readings. Required.

Each reading:

Field	What to send
`metric`	The id of a defined metric. Required.
`value`	The number. Required.
`date`	The day the number is for, such as 2026-10-29
`at`	A full timestamp, in place of `date`
`labels`	Which part of the metric the number is for, such as `{"plan": "pro"}`. Works on any metric.
`key`	Makes sending again safe when a metric has more than one reading a day