> ## Documentation Index > Fetch the complete documentation index at: https://docs.mangrovesystems.com/llms.txt > Use this file to discover all available pages before exploring further. # Correct a data point value > Substitutes the value of one data point, addressed by its data point type slug within an event. Use it to replace a wrong reading, or to set a value where none was recorded. The server records the previous value as `from_value`, which is null when no reading existed, and creates the data point on the event if it did not exist yet. Each call appends to the data point's correction history, so the original reading stays readable. Setting a value does not recalculate anything downstream. A batch that was already generated keeps the value it was generated with. **Replays return 200, new corrections return 201.** A call is treated as a replay when the data point's latest correction has both the same `method` and the same value, in which case that existing correction is returned and nothing is written. Values are compared after normalization, so `"10.2"`, `10.2` and a stored `10.20` all match. Note that `method` participates in this check: retrying with a different `method` writes a second correction rather than matching the first. Requires corrections to be enabled on the account. ## OpenAPI ````yaml PUT /projects/{project_id}/events/{event_id}/data_points/{slug}/value openapi: 3.1.0 info: title: Mangrove - API version: 1.1.0 servers: - url: https://app.gomangrove.com/api/v1 security: - sec0: [] paths: /projects/{project_id}/events/{event_id}/data_points/{slug}/value: put: summary: Correct a data point value description: >- Substitutes the value of one data point, addressed by its data point type slug within an event. Use it to replace a wrong reading, or to set a value where none was recorded. The server records the previous value as `from_value`, which is null when no reading existed, and creates the data point on the event if it did not exist yet. Each call appends to the data point's correction history, so the original reading stays readable. Setting a value does not recalculate anything downstream. A batch that was already generated keeps the value it was generated with. **Replays return 200, new corrections return 201.** A call is treated as a replay when the data point's latest correction has both the same `method` and the same value, in which case that existing correction is returned and nothing is written. Values are compared after normalization, so `"10.2"`, `10.2` and a stored `10.20` all match. Note that `method` participates in this check: retrying with a different `method` writes a second correction rather than matching the first. Requires corrections to be enabled on the account. operationId: correct-a-data-point-value parameters: - name: project_id in: path schema: type: string required: true - name: event_id in: path schema: type: string required: true description: >- Unique ID of the event in the `evt_XXXX` syntax. For example: `evt_DLnYvzbjSujNAvXE` - name: slug in: path schema: type: string required: true description: >- Data point type slug on the event's event type. For example: `ambient-temperature-c`. A slug the event type does not define returns 422. requestBody: content: application/json: schema: type: object required: - value properties: value: description: >- The corrected value. Number, string or boolean, matching the data point type. Required; a null value returns 400. oneOf: - type: number - type: string - type: boolean method: type: string default: manual_entry description: >- How the value was arrived at, recorded on the correction and shown in the audit trail. Free text, and it also decides whether a repeat call is treated as a replay. notes: type: string description: Free-text justification stored with the correction. expect: type: string enum: - gap - existing description: >- Optional guard on the state you believe the data point is in. Pass `gap` to require that it is currently empty, or `existing` to require that it already has a value. A mismatch returns 422 and writes nothing. Because this endpoint creates the data point when the slug has no value yet, `existing` is the guard that stops a wrong slug or event ID from silently manufacturing data. It only tests empty against non-empty, so it will not detect a value that changed from one number to another. examples: Correct an existing reading: value: value: 12.4 expect: existing notes: Sensor drift confirmed against the calibration log. Fill a gap: value: value: 0 method: zero_fill expect: gap notes: Meter offline for maintenance; no flow during the window. responses: '200': description: Replay of the latest correction; nothing was written. content: application/json: examples: Result: value: id: sub_9TnpQxL2mKdRvWs4 data_point_id: in_kiIuaGIUqRxWUmTY stage: ingestion source: api method: manual_entry origin: substituted from_value: 14.9 to_value: 12.4 notes: Sensor drift confirmed against the calibration log. rule: null created_by: Aaron Rosenberg created_at: '2026-07-21T14:02:55.000Z' schema: $ref: '#/components/schemas/DataPointCorrection' '201': description: Correction applied. content: application/json: examples: Result: value: id: sub_9TnpQxL2mKdRvWs4 data_point_id: in_kiIuaGIUqRxWUmTY stage: ingestion source: api method: manual_entry origin: substituted from_value: 14.9 to_value: 12.4 notes: Sensor drift confirmed against the calibration log. rule: null created_by: Aaron Rosenberg created_at: '2026-07-21T14:02:55.000Z' schema: $ref: '#/components/schemas/DataPointCorrection' '400': description: '400' content: application/json: examples: Result: value: errors: - message: A value is required '403': description: >- Corrections are not enabled on the account, or the token does not have Data Collection write permission. content: application/json: examples: Corrections not enabled: value: errors: - message: Corrections are not enabled Insufficient permission: value: errors: - message: You are not authorized to perform this action '422': description: '422' content: application/json: examples: Unknown slug: value: errors: - message: Unknown data point type 'ambient-temp' Expected a gap: value: errors: - message: This data point already has a value Expected a value: value: errors: - message: This data point has no value to correct Unknown expectation: value: errors: - message: Unknown expectation 'empty' (use 'gap' or 'existing') deprecated: false components: schemas: DataPointCorrection: type: object description: One entry in a data point's correction history. properties: id: type: string description: Correction friendly ID. example: sub_9TnpQxL2mKdRvWs4 data_point_id: type: string description: Friendly ID of the corrected data point. example: in_kiIuaGIUqRxWUmTY stage: type: string enum: - ingestion - value_stream description: >- `ingestion` corrections change the data point's value, which every model and report reads. Corrections written through this API are always `ingestion`. `value_stream` corrections are overrides scoped to a single value stream and leave the shared value untouched; they cannot be created here. source: type: string enum: - manual - api - rule - transformation description: >- Where the correction came from. Corrections written through this API are `api`. method: type: string description: >- How the value was arrived at, as supplied by the caller. Reverts are recorded with the reserved method `revert`. example: manual_entry origin: type: string enum: - substituted - imputed - reverted description: >- `substituted` changed an existing reading. `imputed` set a value where none was recorded, and is the case the Events table calls **Value was missing**. `reverted` restored the previous value. from_value: description: The value before this entry. Null when no reading existed. oneOf: - type: number - type: string - type: boolean - type: 'null' to_value: description: The value after this entry. oneOf: - type: number - type: string - type: boolean - type: 'null' notes: type: - string - 'null' rule: type: - object - 'null' description: >- The data rule that wrote this correction. Null for manual and API corrections. properties: name: type: string friendly_id: type: string created_by: type: - string - 'null' description: Name of the user the correction is attributed to. created_at: type: string format: date-time securitySchemes: sec0: type: apiKey in: header name: Authorization x-bearer-format: '' ````