AI observability

For instructions on how to authenticate to use this endpoint, see API overview.

Endpoints

POST

Create llm analytics text repr

Generate a human-readable text representation of an LLM trace event.

This endpoint converts AI observability events ($ai_generation, $ai_span, $ai_embedding, or $ai_trace) into formatted text representations suitable for display, logging, or analysis.

Supported Event Types:

  • $ai_generation: Individual LLM API calls with input/output messages
  • $ai_span: Logical spans with state transitions
  • $ai_embedding: Embedding generation events (text input → vector)
  • $ai_trace: Full traces with hierarchical structure

Options:

  • max_length: Maximum character count (default: 2000000)
  • truncated: Enable middle-content truncation within events (default: true)
  • truncate_buffer: Characters at start/end when truncating (default: 1000)
  • include_markers: Use interactive markers vs plain text indicators (default: true)
    • Frontend: set true for <<<TRUNCATED|base64|...>>> markers
    • Backend/LLM: set false for ... (X chars truncated) ... text
  • collapsed: Show summary vs full trace tree (default: false)
  • include_hierarchy: Include tree structure for traces (default: true)
  • max_depth: Maximum depth for hierarchical rendering (default: unlimited)
  • tools_collapse_threshold: Number of tools before auto-collapsing list (default: 5)
    • Tool lists >5 items show <<<TOOLS_EXPANDABLE|...>>> marker for frontend
    • Or [+] AVAILABLE TOOLS: N for backend when include_markers: false
  • include_line_numbers: Prefix each line with line number like L001:, L010: (default: false)

Use Cases:

  • Frontend display: truncated: true, include_markers: true, include_line_numbers: true
  • Backend LLM context (summary): truncated: true, include_markers: false, collapsed: true
  • Backend LLM context (full): truncated: false

The response includes the formatted text and metadata about the rendering.

Required API key scopes

llm_analytics:write

Request parameters

  • event_type
  • data
  • options

Response


Example request

POST /api/projects/:project_id/llm_analytics/text_repr
export POSTHOG_PERSONAL_API_KEY=[your personal api key]
curl
-H 'Content-Type: application/json'\
-H "Authorization: Bearer $POSTHOG_PERSONAL_API_KEY" \
<ph_app_host>/api/projects/:project_id/llm_analytics/text_repr/\
-d event_type=undefined,\
-d data=undefined

Example response

Status 200
RESPONSE
{
"text": "INPUT:\n\n[1] USER\n\nWhat is the capital of France?\n\n...",
"metadata": {
"event_type": "$ai_generation",
"event_id": "gen_123",
"rendering": "detailed",
"char_count": 150,
"truncated": false
}
}
Status 400
Status 500
Status 503