Users

Register a user

Create or update a user profile and store optional traits or handles (e.g. URLs, social profiles, or notes). This endpoint is idempotent — if the user already exists, the existing profile will be merged with the new data.

PUT /register

Purpose

Register users into the Fastino Personalization API so agents can begin ingesting context and retrieving personalized summaries.
You can call this endpoint when a user signs up, changes profile information, or when metadata such as timezone or communication preferences updates.

Endpoint

Headers

Request Body

Field	Type	Required	Description
`user_id`	string	✅ Yes	A unique identifier for the user.
`traits`	object	Optional	Metadata about the user (name, timezone, URLs, handles, notes, etc.).
`purpose`	string	Optional	Optional description of the user’s role or the purpose of this personalization context.

Example Request

{
  "user_id": "usr_42af7c",
  "traits": {
    "name": "Ash Lewis",
    "locale": "en-US",
    "timezone": "America/Los_Angeles",
    "personal_urls": ["https://ash.example.com", "https://fastino.ai"],
    "linkedin_url": "https://www.linkedin.com/in/ashlewis",
    "twitter_handle": "@ash_csx",
    "github_handle": "ash-lewis",
    "notes": "Founder/engineer; prefers concise comms"
  },
  "purpose": "Used by an AI calendar assistant to manage meetings and timezones"
}

Example cURL

curl -X PUT "https://api.fastino.ai/register" \
  -H "Authorization: x-api-key: sk_test_123" \
  -H "Content-Type: application/json" \
  -d '{
    "user_id": "usr_42af7c",
    "traits": {
      "name": "Ash Lewis",
      "timezone": "America/Los_Angeles",
      "notes": "Founder/engineer; prefers concise comms"
    }
  }'

Example Response

{
  "user_id": "usr_42af7c",
  "created_at": "2025-10-11T16:05:00Z",
  "status": "active"
}

Behavior

If the user already exists, traits will be merged into the existing profile.
You can safely re-send this request to synchronize updated user information.
Fields omitted from a subsequent request will not delete previous values.

Response Fields

Field	Type	Description
`user_id`	string	The unique user ID created or updated.
`created_at`	string	ISO 8601 timestamp of registration or update.
`status`	string	Current user status (`active`, `pending`, or `archived`).

Error Responses

HTTP Code	Error Code	Description
`400`	`INVALID_REQUEST`	The request body is malformed or missing required fields.
`401`	`UNAUTHORIZED`	Invalid or missing API token.
`500`	`SERVER_ERROR`	Internal error — retry with exponential backoff.

Example:

{
  "error": {
    "code": "INVALID_REQUEST",
    "message": "Missing required field: user_id"
  }
}

Best Practices

Use consistent, unique user_id values across all integrations and tools.
Include relevant metadata like timezone and locale to improve contextual predictions.
Update user traits periodically as the user’s context or behavior changes.
Store your API key securely and never expose it in client-side applications.

Related Endpoints

Endpoint	Description
POST `/delete`	Delete all personalization data for a user.
POST `/ingest`	Ingest new data or events for a registered user.
GET `/summary`	Retrieve the user’s personalized summary.

Summary:
Use PUT /register to initialize or update user profiles in Fastino. This endpoint forms the foundation for all personalization, enabling downstream ingestion, retrieval, and reasoning.

Run Inference

Delete user data

Join our Discord Community

On this page

Title