OpenFeature Remote Evaluation Protocol (OFREP) v1 compliance — endpoints, request/response format, and interoperability

OFREP Protocol

Flaggr implements the OpenFeature Remote Evaluation Protocol (OFREP) v1, enabling interoperability with any OFREP-compatible client or provider.

What is OFREP?

OFREP is the standard protocol defined by the OpenFeature project for remote flag evaluation. It provides a vendor-neutral API that any feature flag provider can implement, and any OpenFeature SDK can consume.

Vendor Neutral

OFREP means you can switch between flag providers without changing your application code. Any OFREP-compatible SDK works with Flaggr.

Endpoints

Single Flag Evaluation

POST/api/ofrep/v1/evaluate/flags/{key}Bearer token (optional)

Evaluate a single flag by key.

Headers:

Header	Required	Description
`X-Service-Id`	Yes	Service identifier (or `serviceId` query param)
`X-Environment`	No	`development`, `staging`, `production` (default: `development`)
`Authorization`	No	`Bearer` token for authenticated evaluation

Request:

{
  "context": {
    "targetingKey": "user-123",
    "email": "alice@example.com",
    "plan": "enterprise"
  }
}

Response (200):

{
  "key": "checkout-v2",
  "value": true,
  "reason": "TARGETING_MATCH",
  "variant": "enabled",
  "metadata": {
    "evaluatedAt": "2025-07-20T10:30:00Z"
  }
}

Multi-Language Examples

curl -s -X POST https://flaggr.dev/api/ofrep/v1/evaluate/flags/checkout-v2 \
  -H "Authorization: Bearer flg_abc123xxxxxxxxxxxx" \
  -H "Content-Type: application/json" \
  -H "X-Service-Id: web-app" \
  -H "X-Environment: production" \
  -d '{
    "context": {
      "targetingKey": "user-123",
      "email": "alice@example.com",
      "plan": "enterprise"
    }
  }' | jq

Bulk Evaluation

POST/api/ofrep/v1/evaluate/flagsBearer token (optional)

Evaluate multiple flags in a single request.

Request:

{
  "context": {
    "targetingKey": "user-123",
    "plan": "enterprise"
  },
  "flags": ["checkout-v2", "dark-mode", "new-pricing"]
}

Omit flags to evaluate all flags for the service.

Response (200):

{
  "flags": [
    {
      "key": "checkout-v2",
      "value": true,
      "reason": "TARGETING_MATCH",
      "variant": "enabled"
    },
    {
      "key": "dark-mode",
      "value": false,
      "reason": "DEFAULT"
    },
    {
      "key": "new-pricing",
      "value": "tier-b",
      "reason": "VARIANT",
      "variant": "tier-b"
    }
  ]
}

Multi-Language Examples

curl -s -X POST https://flaggr.dev/api/ofrep/v1/evaluate/flags \
  -H "Authorization: Bearer flg_abc123xxxxxxxxxxxx" \
  -H "Content-Type: application/json" \
  -H "X-Service-Id: web-app" \
  -d '{
    "context": {
      "targetingKey": "user-123",
      "plan": "enterprise"
    },
    "flags": ["checkout-v2", "dark-mode", "new-pricing"]
  }' | jq '.flags[] | "\(.key): \(.value) (\(.reason))"'

Server Metadata

GET/api/ofrep/v1/metadata

Returns server capabilities and version information.

Response:

{
  "name": "flaggr",
  "version": "1.0.0",
  "capabilities": {
    "cacheInvalidation": true,
    "flagChangeEvents": true,
    "contextTransform": true
  }
}

OFREP Reasons

Reason	Description
`STATIC`	Statically configured value
`DEFAULT`	Default value returned
`TARGETING_MATCH`	Targeting rule matched
`SPLIT`	Variant percentage split
`CACHED`	Cached evaluation result
`DISABLED`	Flag is disabled
`ERROR`	Evaluation error
`UNKNOWN`	Unknown reason

Error Responses

OFREP defines standard error codes:

{
  "key": "nonexistent-flag",
  "errorCode": "FLAG_NOT_FOUND",
  "errorDetails": "Flag 'nonexistent-flag' not found in service 'web-app'",
  "reason": "ERROR"
}

Error Code	HTTP Status	Description
`PROVIDER_NOT_READY`	503	Service initializing
`FLAG_NOT_FOUND`	404	Flag key doesn't exist
`PARSE_ERROR`	400	Invalid request format
`TYPE_MISMATCH`	400	Value type doesn't match
`INVALID_CONTEXT`	400	Context validation failed
`GENERAL`	500	Unexpected error

Using with OpenFeature SDKs

Any OpenFeature OFREP provider works with Flaggr.

import { OpenFeature } from "@openfeature/server-sdk";
import { OFREPProvider } from "@openfeature/ofrep-provider";
 
const provider = new OFREPProvider({
  baseUrl: "https://flaggr.dev/api/ofrep/v1",
  headers: {
    "X-Service-Id": "web-app",
    "Authorization": "Bearer flg_abc123xxxxxxxxxxxx",
  },
});
 
OpenFeature.setProvider(provider);
const client = OpenFeature.getClient();
 
const isEnabled = await client.getBooleanValue("checkout-v2", false, {
  targetingKey: "user-123",
});
console.log(`checkout-v2 enabled: ${isEnabled}`);