Metric and sample-size movement
real_or_samplingDetermine whether a metric's latest departure persists after adjusting for its historical relationship with sample size. Use with aligned metric and denominator arrays; needs at least ten pairs.
Instructions
Review whether the latest numeric metric departure persists after accounting for its historical linear association with measurement sample size. Use when both a dashboard metric and its coverage denominator are available; choose did_it_change when no denominator is known. Requires at least ten aligned pairs; shorter valid arrays return NOT_ENOUGH_HISTORY. The latest pair is excluded from the historical fit. Returns verdict, assessment, reading and, when estimable, metric_delta in input units, standardized departures, sample_size_change_pct as a percent of the historical median, fit and departure_after_conditioning. Prefer assessment/validity over legacy REAL or SAMPLING_ARTIFACT labels: linear association neither proves a sampling cause nor excludes confounding. Constant or weakly related histories can return UNCLEAR and null standardized values. Unequal array lengths or nonpositive sample sizes return a tool error.
Input Schema
| Name | Required | Description | Default |
|---|---|---|---|
| values | Yes | Chronological metric readings in consistent units, one per sample_sizes entry. At least 10 aligned pairs are needed; all earlier pairs form the reference for the latest reading. | |
| sample_sizes | Yes | Positive measurement denominators aligned one-for-one with values. Equal array length is required. Zero coverage is missing data, not a valid denominator; economic trading volume is not measurement coverage. |
Output Schema
| Name | Required | Description | Default |
|---|---|---|---|
| fit | No | Historical linear association, when estimable. | |
| error | No | Validation or computation failure message; inspect MCP isError or the HTTP status. | |
| method | No | Descriptive denominator-conditioning method. | |
| caveats | No | Ordered statements or identifiers. | |
| n_pairs | No | Number of aligned metric/measurement-denominator pairs. | |
| reading | No | Explanation and limits of the result. | |
| verdict | No | Legacy descriptive result code. | |
| validity | No | Descriptive assessment, not a probability or statistical certificate. | |
| guarantee | No | No statistical or market-performance guarantee is made. | |
| is_causal | No | Association does not establish causality. | |
| assessment | No | Preferred interpretation of the legacy verdict. | |
| metric_now | No | Latest metric in input units. | |
| metric_delta | No | Latest metric minus historical median, in input units. | |
| sample_size_now | No | Latest declared measurement denominator. | |
| metric_departure | No | Robust standardized latest metric departure. Null means unavailable or not applicable, never zero. | |
| sample_size_departure | No | Robust standardized denominator departure. Null means unavailable or not applicable, never zero. | |
| zero_reference_spread | No | Historical metric MAD is zero. | |
| sample_size_change_pct | No | Denominator change as percent of its historical median. | |
| denominator_extrapolation | No | Latest denominator falls outside the historical range. | |
| departure_after_conditioning | No | Robust standardized latest residual after linear conditioning. Null means unavailable or not applicable, never zero. |