Activities

What is an Activity?

An Activity is a single log entry that records something that happened during a session. Activities answer:

“What did the agent do, and in what order?”

They form a complete, inspectable timeline of a session’s execution.

Why Activities exist

Agents in production need more than a final status. You need to know:

When did execution start?
What messages did the agent produce?
When did it request input?
When was that input resolved?
Did it write results to a sink?
What state changes occurred?

Activities provide this without parsing logs, tracing calls, or instrumenting your framework.

Activity types

Type	Description
`session_started`	Session was created and execution began
`session_ended`	Session completed or failed
`message`	Agent produced a human-readable message
`input_request_created`	Agent requested input from a human
`input_request_resolved`	Human responded to an input request
`sink_item_created`	Agent wrote an item to a sink
`state_updated`	Session state was updated

Activity sources

Each activity has a source indicating who created it:

Source	Description
`system`	Created automatically by OpenSink (e.g. session start/end, input request lifecycle)
`agent`	Created by your agent code (e.g. messages, progress updates)
`user`	Created by a human (e.g. manual notes)

Structure

Field	Description
`type`	What happened
`source`	Who created it — `system`, `agent`, or `user`
`message`	Human-readable description
`payload`	Optional structured data
`related_entity_id`	Optional link to another entity (e.g. an input request ID, a sink item ID)
`links`	Optional list of associated links
`session_id`	The session this activity belongs to
`agent_id`	The agent that owns this session

Automatic activities

OpenSink creates some activities automatically:

session_started — when a session is created
session_ended — when a session status becomes completed or failed
input_request_created — when an input request is created
input_request_resolved — when an input request is resolved

You don’t need to log these yourself.

Creating activities from your agent

Your agent can log its own activities during execution:

curl -X POST https://api.opensink.com/api/v1/agent-session-activities \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer YOUR_API_TOKEN" \
  -d '{
    "session_id": "SESSION_ID",
    "agent_id": "AGENT_ID",
    "type": "message",
    "source": "agent",
    "message": "Analyzed 15 articles. Found 3 relevant to portfolio.",
    "payload": {
      "articles_analyzed": 15,
      "relevant_count": 3
    }
  }'

This makes the agent’s progress visible without requiring a custom UI.

Viewing activities

Activities are listed in reverse chronological order and can be filtered by:

session_id — activities for a specific session
agent_id — activities across all sessions for an agent
type — only specific activity types
source — only system, agent, or user activities

curl "https://api.opensink.com/api/v1/agent-session-activities?session_id=SESSION_ID" \
  -H "Authorization: Bearer YOUR_API_TOKEN"

What Activities are not

Activities are not:

debug logs
LLM traces
metrics or telemetry
a replacement for structured logging

They are high-level, meaningful events that tell you what an agent did during a session.

When to use Activities

Activities are useful when:

you need to understand what happened during a session
you want agent progress visible in the UI
you need an audit trail for compliance
debugging requires knowing the sequence of events

If your agent does something worth knowing about — log an activity.

Getting started

Integrations

Core Concepts

Agents

Examples & Use Cases

What is an Activity?

Why Activities exist

Activity types

Activity sources

Structure

Automatic activities

Creating activities from your agent

Viewing activities

What Activities are not

When to use Activities

​What is an Activity?

​Why Activities exist

​Activity types

​Activity sources

​Structure

​Automatic activities

​Creating activities from your agent

​Viewing activities

​What Activities are not

​When to use Activities

What is an Activity?

Why Activities exist

Activity types

Activity sources

Structure

Automatic activities

Creating activities from your agent

Viewing activities

What Activities are not

When to use Activities