Manual capture LLM analytics installation

If you're using a different server-side SDK or prefer to use the API, you can manually capture the data by calling the capture method or using the capture API.

Capture via API

curl -X POST "https://us.i.posthog.com/i/v0/e/" \
        -H "Content-Type: application/json" \
        -d '{
            "api_key": "<ph_project_api_key>",
            "event": "$ai_generation",
            "properties": {
                "distinct_id": "user_123",
                "$ai_trace_id": "trace_id_here",
                "$ai_model": "gpt-4o-mini",
                "$ai_provider": "openai",
                "$ai_input": [{"role": "user", "content": "Tell me a fun fact about hedgehogs"}],
                "$ai_input_tokens": 10,
                "$ai_output_choices": [{"role": "assistant", "content": "Hedgehogs have around 5,000 to 7,000 spines on their backs!"}],
                "$ai_output_tokens": 20,
                "$ai_latency": 1.5
            }
        }'

Event Properties

Each event type has specific properties. See the tabs below for detailed property documentation for each event type.

A generation is a single call to an LLM.

Event name: $ai_generation

Core properties

PropertyDescription
$ai_trace_id

The trace ID (a UUID to group AI events) like conversation_id
Must contain only letters, numbers, and special characters: -, _, ~, ., @, (, ), !, ', :, |
Example: d9222e05-8708-41b8-98ea-d4a21849e761

$ai_session_id

(Optional) Groups related traces together. Use this to organize traces by whatever grouping makes sense for your application (user sessions, workflows, conversations, or other logical boundaries).
Example: session-abc-123, conv-user-456

$ai_span_id

(Optional) Unique identifier for this generation

$ai_span_name

(Optional) Name given to this generation
Example: summarize_text

$ai_parent_id

(Optional) Parent span ID for tree view grouping

$ai_model

The model used
Example: gpt-5-mini

$ai_provider

The LLM provider
Example: openai, anthropic, gemini

$ai_input

List of messages sent to the LLM. Each message should have a role property with one of: "user", "system", or "assistant"
Example:

[
  {
    "role": "user",
    "content": [
      {
        "type": "text",
        "text": "What's in this image?"
      },
      {
        "type": "image",
        "image": "https://example.com/image.jpg"
      },
      {
        "type": "function",
        "function": {
          "name": "get_weather",
          "arguments": {
            "location": "San Francisco"
          }
        }
      }
    ]
  }
]
$ai_input_tokens

The number of tokens in the input (often found in response.usage)

$ai_output_choices

List of response choices from the LLM. Each choice should have a role property with one of: "user", "system", or "assistant"
Example:

[
  {
    "role": "assistant",
    "content": [
      {
        "type": "text",
        "text": "I can see a hedgehog in the image."
      },
      {
        "type": "function",
        "function": {
          "name": "get_weather",
          "arguments": {
            "location": "San Francisco"
          }
        }
      }
    ]
  }
]
$ai_output_tokens

The number of tokens in the output (often found in response.usage)

$ai_latency

(Optional) The latency of the LLM call in seconds

$ai_http_status

(Optional) The HTTP status code of the response

$ai_base_url

(Optional) The base URL of the LLM provider
Example: https://api.openai.com/v1

$ai_request_url

(Optional) The full URL of the request made to the LLM API
Example: https://api.openai.com/v1/chat/completions

$ai_is_error

(Optional) Boolean to indicate if the request was an error

$ai_error

(Optional) The error message or object

Cost properties

Cost properties are optional as we can automatically calculate them from model and token counts. If you want, you can provide your own cost properties or custom pricing instead.

Pre-calculated costs

PropertyDescription
$ai_input_cost_usd

(Optional) The cost in USD of the input tokens

$ai_output_cost_usd

(Optional) The cost in USD of the output tokens

$ai_request_cost_usd

(Optional) The cost in USD for the requests

$ai_web_search_cost_usd

(Optional) The cost in USD for the web searches

$ai_total_cost_usd

(Optional) The total cost in USD (sum of all cost components)

Custom pricing

PropertyDescription
$ai_input_token_price

(Optional) Price per input token (used to calculate $ai_input_cost_usd)

$ai_output_token_price

(Optional) Price per output token (used to calculate $ai_output_cost_usd)

$ai_cache_read_token_price

(Optional) Price per cached token read

$ai_cache_write_token_price

(Optional) Price per cached token write

$ai_request_price

(Optional) Price per request

$ai_request_count

(Optional) Number of requests (defaults to 1 if $ai_request_price is set)

$ai_web_search_price

(Optional) Price per web search

$ai_web_search_count

(Optional) Number of web searches performed

Cache properties

PropertyDescription
$ai_cache_read_input_tokens

(Optional) Number of tokens read from cache

$ai_cache_creation_input_tokens

(Optional) Number of tokens written to cache (Anthropic-specific)

Model parameters

PropertyDescription
$ai_temperature

(Optional) Temperature parameter used in the LLM request

$ai_stream

(Optional) Whether the response was streamed

$ai_max_tokens

(Optional) Maximum tokens setting for the LLM response

$ai_tools

(Optional) Tools/functions available to the LLM
Example:

[
  {
    "type": "function",
    "function": {
      "name": "get_weather",
      "parameters": {}
    }
  }
]

Community questions

Was this page useful?

Questions about this page? or post a community question.