launchdarkly Server-Side Evaluation API

Flag evaluation endpoints for server-side SDKs using SDK keys for authentication.

Documentation GitHub OpenAPI

Business capability

Operations 1

Each operation below carries the questions people ask an LLM about it and the instructions they give an agent to run it. Generated by API Evangelist overlay

GET /sdk/evalx/contexts/{contextBase64} Evaluate all flags for a context server-side · Evaluate all flags for a context (GET) #

Ask an LLM

“How do I evaluate every flag for a context using my SDK key?”

“What values would all flags return for this user on the server?”

Tell an agent

Evaluate all flags for context {contextBase64}.

Get server-side flag values for base64 context {contextBase64}.

Documentation

📖

Documentation

https://launchdarkly.com/docs/api

📖

Documentation

https://launchdarkly.com/docs/sdk/relay-proxy

Specifications

⚙

OpenAPI

https://raw.githubusercontent.com/api-evangelist/launchdarkly/refs/heads/main/openapi/launchdarkly-server-side-evaluation-api-openapi.yml

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OpenAPI Specification

openapi: 3.2.0
info:
  title: LaunchDarkly Relay Proxy Server-Side Evaluation API
  description: The LaunchDarkly Relay Proxy is a small Go application that connects to the LaunchDarkly streaming API and proxies that connection to SDK clients within an organization's network. It exposes endpoints for status monitoring, flag evaluation, and SDK streaming that mirror the LaunchDarkly service endpoints. Instead of each server making outbound connections to LaunchDarkly's streaming service, multiple servers connect to the local Relay Proxy which maintains a single upstream connection.
  version: '8.0'
  contact:
    name: LaunchDarkly Support
    url: https://support.launchdarkly.com
  license:
    name: Apache 2.0
    url: https://www.apache.org/licenses/LICENSE-2.0
servers:
- url: http://localhost:8030
  description: Default Relay Proxy instance
tags:
- name: Server-Side Evaluation
  description: Flag evaluation endpoints for server-side SDKs using SDK keys for authentication.
paths:
  /sdk/evalx/contexts/{contextBase64}:
    get:
      operationId: evaluateAllFlagsForContext
      summary: Evaluate all flags for a context (GET)
      description: Evaluates all feature flags for the given context and returns the results. The context is provided as a base64-encoded JSON object in the URL path. Requires an SDK key in the Authorization header.
      tags:
      - Server-Side Evaluation
      security:
      - sdkKeyAuth: []
      parameters:
      - $ref: '#/components/parameters/ContextBase64'
      responses:
        '200':
          description: Successful response with all flag evaluations for the context.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/FlagEvaluations'
        '401':
          description: Unauthorized. The SDK key does not match any environment configured in the Relay Proxy.
        '503':
          description: Service unavailable. The Relay Proxy has not yet received flag data from LaunchDarkly for this environment.
components:
  parameters:
    ContextBase64:
      name: contextBase64
      in: path
      required: true
      description: A base64-encoded JSON representation of the evaluation context.
      schema:
        type: string
  schemas:
    FlagEvaluations:
      type: object
      description: A map of flag keys to their evaluated results for a context.
      additionalProperties:
        $ref: '#/components/schemas/FlagEvaluation'
    FlagEvaluation:
      type: object
      description: The evaluated result of a single feature flag.
      properties:
        value:
          description: The evaluated value of the flag for the given context.
        variation:
          type: integer
          description: The index of the variation that was served.
        version:
          type: integer
          description: The version number of the flag.
        trackEvents:
          type: boolean
          description: Whether analytics events should be tracked for this flag.
        trackReason:
          type: boolean
          description: Whether the evaluation reason should be included in events.
        reason:
          type: object
          description: The reason for the evaluation result.
          properties:
            kind:
              type: string
              description: The kind of evaluation reason.
              enum:
              - 'OFF'
              - FALLTHROUGH
              - TARGET_MATCH
              - RULE_MATCH
              - PREREQUISITE_FAILED
              - ERROR
  securitySchemes:
    sdkKeyAuth:
      type: apiKey
      in: header
      name: Authorization
      description: Server-side SDK key for authenticating with the Relay Proxy.
    mobileKeyAuth:
      type: apiKey
      in: header
      name: Authorization
      description: Mobile SDK key for authenticating with the Relay Proxy.
externalDocs:
  description: Relay Proxy Documentation
  url: https://launchdarkly.com/docs/sdk/relay-proxy