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Overview

Add or update custom properties on existing requests. Properties are key-value pairs that allow you to attach metadata, tags, or contextual information to requests after they’ve been created. This is useful for post-hoc categorization, debugging, and analytics.

Endpoint

string
required
PUT
string
required
/v1/request//property

Authentication

Requires API key authentication via the Authorization header:

Path Parameters

string
required
The unique identifier of the request to update

Request Body

string
required
The property key/name. Must be a string.Examples:
  • "environment"
  • "user_tier"
  • "feature_flag"
  • "conversation_id"
  • "customer_id"
string
required
The property value. Must be a string.Examples:
  • "production"
  • "premium"
  • "enabled"
  • "conv_123"
  • "cust_456"

Response

Returns a success or error response.
null
Always null on success
string
Error message if the request failed, otherwise null

Examples

Add Single Property

Add an environment tag:

Update Existing Property

Update a property value (same key, new value):

Add Multiple Properties

Add multiple properties by making multiple requests:

Using in Code

Response Examples

Success Response

Error Response

Use Cases

Post-Processing Categorization

Tag requests after analysis:

Customer Tracking

Link requests to customer accounts:

A/B Test Annotation

Mark requests with experiment variants:

Error Classification

Tag failed requests with error categories:

Feature Flag Tracking

Track which features were enabled:

Quality Review Workflow

Manage review status:

Cost Allocation

Tag requests for cost tracking:

Query by Properties

Filter requests by custom properties:

Property Naming Best Practices

  1. Use snake_case: customer_id instead of customerId or CustomerID
  2. Be consistent: Use the same property names across your application
  3. Namespace when needed: feature_new_ui instead of just new_ui
  4. Keep keys short: env vs environment_name_and_region
  5. Document your schema: Maintain a list of standard properties

Example Property Schema

Notes

  • Properties are stored as string key-value pairs
  • If a property key already exists, the value will be updated
  • Properties are immediately available in queries and analytics
  • Maximum recommended property key length: 100 characters
  • Maximum recommended property value length: 1000 characters
  • Properties can be set during request creation via Helicone headers or after the fact via this API
  • Use properties in combination with feedback and scores for comprehensive request tagging

Comparison with Request-Time Properties

You can also set properties when making requests using Helicone headers:
Use this API endpoint when:
  • You need to add properties after a request has been made
  • Properties are determined through post-processing or analysis
  • You’re categorizing or tagging historical data
  • Properties depend on the response or subsequent events
Use request-time headers when:
  • You know the properties at request time
  • Properties are part of your application context
  • You want to minimize API calls