AgentObs - LLM Agent Observability for Elixir
I’m excited to share AgentObs, a new library for instrumenting LLM agentic
applications in Elixir with rich observability!
What is AgentObs?
AgentObs provides a simple, idiomatic interface for tracking agent loops, tool
calls, LLM requests, and prompts in your Elixir applications. It uses native
:telemetry events and translates them to OpenTelemetry spans with
OpenInference semantic conventions.
Key Features:
High-level instrumentation helpers - trace_agent/3,trace_tool/3,
trace_llm/3,trace_prompt/3
Optional ReqLLM integration - Automatic instrumentation with token tracking
and streaming support
Pluggable backend architecture - Phoenix (OpenInference), Generic
OpenTelemetry, or custom handlers
Rich metadata tracking - Token usage, costs, tool calls, and more
Built on OTP - Supervised handlers with fault tolerance
Quick Example
defmodule MyApp.WeatherAgent do
def get_forecast(city) do
AgentObs.trace_agent("weather_forecast", %{input: "What's the weather in #{city}?"}, fn ->
# Call LLM to determine tool to use
{:ok, _response, _metadata} =
AgentObs.trace_llm("gpt-4o", %{
input_messages: [%{role: "user", content: "Get weather for #{city}"}]
}, fn ->
response = call_openai(...)
{:ok, response, %{
output_messages: [%{role: "assistant", content: response}],
tokens: %{prompt: 50, completion: 25, total: 75}
}}
end)
# Execute the tool
{:ok, weather_data} =
AgentObs.trace_tool("get_weather_api", %{arguments: %{city: city}}, fn ->
{:ok, %{temp: 72, condition: "sunny"}}
end)
{:ok, "The weather in #{city} is #{weather_data.condition}", %{
tools_used: ["get_weather_api"]
}}
end)
end
end
ReqLLM Integration
For apps using ReqLLM, AgentObs provides helpers
that automatically extract tokens, tool calls, and more:
# Non-streaming
{:ok, response} =
AgentObs.ReqLLM.trace_generate_text(
"anthropic:claude-3-5-sonnet",
[%{role: "user", content: "Hello!"}]
)
# Streaming
{:ok, stream_response} =
AgentObs.ReqLLM.trace_stream_text(
"anthropic:claude-3-5-sonnet",
[%{role: "user", content: "Tell me a story"}]
)
Visualization
Use with Arize Phoenix to get beautiful trace visualization with chat messages,
token usage, and nested spans:
Links
Hex: agent_obs | Hex
Docs: agent_obs v0.1.0 — Documentation
GitHub:
