> ## Documentation Index > Fetch the complete documentation index at: https://opendata.dev/docs/llms.txt > Use this file to discover all available pages before exploring further. # List label names > Return the sorted list of all label names present in the database. Optionally filtered by series selectors and/or a time range. When `match[]` selectors are provided, only label names from series matching those selectors are returned. When `start` and/or `end` are provided, only series with samples in that time range are considered. Also accepts POST with a `application/x-www-form-urlencoded` body containing the same parameters. ## OpenAPI ````yaml /openapi/timeseries.yaml get /api/v1/labels openapi: 3.1.0 info: title: OpenData Timeseries API version: 1.0.0 description: | Prometheus-compatible HTTP API for the OpenData Timeseries service. Query endpoints accept both GET (query parameters) and POST (application/x-www-form-urlencoded body) with identical parameters. This spec documents the GET form; POST is always available as an alternative for large queries that may exceed URL character limits. ## Timestamp formats All timestamp parameters accept either **RFC 3339** format (e.g. `2024-01-20T00:00:00Z`) or **Unix seconds** as a float (e.g. `1705708800` or `1705708800.123`). Timestamps in responses are always Unix seconds. ## Duration format Duration parameters use PromQL duration syntax: an integer followed by a unit suffix. Supported units are `ms` (milliseconds), `s` (seconds), `m` (minutes), `h` (hours), `d` (days), `w` (weeks), and `y` (years). Examples: `30s`, `5m`, `1h30m`. ## Sample values Sample values are always transferred as JSON strings (not numbers) to allow special values such as `"NaN"`, `"+Inf"`, and `"-Inf"`. ## Response envelope Every JSON response follows a common envelope: ```json { "status": "success" | "error", "data": , "errorType": "", "error": "", "warnings": [""] } ``` The `error` and `errorType` fields are only present when `status` is `"error"`. The `warnings` array may be present on successful responses when the query engine has non-fatal issues to report (e.g. partial results due to unavailable shards). servers: - url: http://localhost:9090 description: Local development server security: [] paths: /api/v1/labels: get: summary: List label names description: | Return the sorted list of all label names present in the database. Optionally filtered by series selectors and/or a time range. When `match[]` selectors are provided, only label names from series matching those selectors are returned. When `start` and/or `end` are provided, only series with samples in that time range are considered. Also accepts POST with a `application/x-www-form-urlencoded` body containing the same parameters. operationId: listLabels parameters: - name: match[] in: query required: false description: | Optional series selectors to filter which label names are returned. When provided, only label names that appear on series matching at least one of these selectors are included. Multiple selectors are combined with logical OR. schema: type: array items: type: string style: form explode: true - name: start in: query required: false description: | Start timestamp to limit the time range considered. Only label names from series with samples within `[start, end]` are returned. RFC 3339 or Unix seconds. schema: type: string - name: end in: query required: false description: | End timestamp to limit the time range considered. RFC 3339 or Unix seconds. schema: type: string - name: limit in: query required: false description: | Maximum number of label names to return. A value of `0` disables the limit. schema: type: integer minimum: 0 responses: '200': description: | Sorted list of label names as strings. Always includes built-in labels like `__name__` if any metric data exists. content: application/json: schema: $ref: '#/components/schemas/LabelsResponse' example: status: success data: - __name__ - instance - job '400': description: | Bad request. A `match[]` selector is malformed or a parameter is invalid. The `errorType` will be `bad_data`. content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' '500': description: Internal server error. The `errorType` will be `internal`. content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' '503': description: | Service unavailable. The `errorType` will be `unavailable`. content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' components: schemas: LabelsResponse: type: object description: | Response for the label names endpoint (`/api/v1/labels`). On success, `data` contains a sorted array of label name strings. properties: status: type: string enum: - success - error data: type: array items: type: string description: | Alphabetically sorted list of label names. Includes built-in labels like `__name__` if any metric data exists. error: type: string description: Human-readable error message (present when status is `error`). errorType: type: string description: Error category (present when status is `error`). required: - status ErrorResponse: type: object description: | Prometheus-compatible error response. Returned for all non-2xx responses. The `errorType` indicates the category: - `bad_data` (HTTP 400/422): The request was malformed or the expression could not be executed. - `internal` (HTTP 500): An unexpected server-side error occurred. - `unavailable` (HTTP 503): The server is temporarily unable to handle the request due to backpressure or a query timeout. properties: status: type: string example: error errorType: type: string description: | Error category. Maps to HTTP status codes: - `bad_data` → 400 or 422 - `internal` → 500 - `unavailable` → 503 enum: - bad_data - internal - unavailable error: type: string description: Human-readable error message describing what went wrong. required: - status - errorType - error ````