Custom Metrics

Custom Metrics for Configs

Full lifecycle management of custom business metrics: create metric definitions via API, track events via SDK, retrieve metric data, and manage metrics programmatically.

Prerequisites

• LaunchDarkly SDK initialized (see sdk)
• LaunchDarkly API token with writer role for metric management
• Understanding of built-in agent metrics (see built-in-metrics)

API Key Detection

Before prompting the user for an API key, try to detect it automatically:

1. Check Claude MCP config - Read ~/.claude/config.json and look for mcpServers.launchdarkly.env.LAUNCHDARKLY_API_KEY
2. Check environment variables - Look for LAUNCHDARKLY_API_KEY, LAUNCHDARKLY_API_TOKEN, or LD_API_KEY
3. Prompt user - Only if detection fails, ask the user for their API key

import os
import json
from pathlib import Path

def get_launchdarkly_api_key():
    """Auto-detect LaunchDarkly API key from Claude config or environment."""
    # 1. Check Claude MCP config
    claude_config = Path.home() / ".claude" / "config.json"
    if claude_config.exists():
        try:
            config = json.load(open(claude_config))
            api_key = config.get("mcpServers", {}).get("launchdarkly", {}).get("env", {}).get("LAUNCHDARKLY_API_KEY")
            if api_key:
                return api_key
        except (json.JSONDecodeError, IOError):
            pass

    # 2. Check environment variables
    for var in ["LAUNCHDARKLY_API_KEY", "LAUNCHDARKLY_API_TOKEN", "LD_API_KEY"]:
        if os.environ.get(var):
            return os.environ[var]

    return None

Metrics Lifecycle Overview

1. Create Metric (API)

Required fields for numeric custom metrics:

• successCriteria - Must be one of: "HigherThanBaseline", "LowerThanBaseline"
• unit - e.g., "count", "percent", "milliseconds"

The API will return 400 Bad Request if these are missing for numeric metrics.

import requests
import os

def create_metric(
    project_key: str,
    metric_key: str,
    name: str,
    kind: str = "custom",
    is_numeric: bool = True,
    unit: str = "count",
    success_criteria: str = "HigherThanBaseline",
    event_key: str = None,
    description: str = None
):
    """Create a new metric definition in LaunchDarkly."""
    API_TOKEN = os.environ.get("LAUNCHDARKLY_API_TOKEN")

    url = f"https://app.launchdarkly.com/api/v2/metrics/{project_key}"

    payload = {
        "key": metric_key,
        "name": name,
        "kind": kind,
        "isNumeric": is_numeric,
        "eventKey": event_key or metric_key
    }

    # Unit and successCriteria are required for numeric custom metrics
    if is_numeric and kind == "custom":
        payload["unit"] = unit
        payload["successCriteria"] = success_criteria

    if description:
        payload["description"] = description

    headers = {
        "Authorization": API_TOKEN,
        "Content-Type": "application/json"
    }

    response = requests.post(url, json=payload, headers=headers)

    if response.status_code == 201:
        print(f"[OK] Created metric: {metric_key}")
        return response.json()
    elif response.status_code == 409:
        print(f"[INFO] Metric already exists: {metric_key}")
        return None
    else:
        print(f"[ERROR] Failed to create metric: {response.status_code}")
        print(f"        {response.text}")
        return None

Metric Kinds:

• custom - Track any event (most common for agent metrics)
• pageview - Track page views
• click - Track click events

Success Criteria (for numeric metrics):

• HigherThanBaseline - Higher values are better (e.g., revenue, satisfaction)
• LowerThanBaseline - Lower values are better (e.g., errors, latency)

Common Units:

• count - Generic count
• milliseconds - Time duration
• percent - Percentage values
• dollars - Currency

2. Track Events (SDK)

Once the metric is created, track events using the SDK:

from ldclient import Context
from ldclient.config import Config
import ldclient

# Initialize (see sdk for details)
ldclient.set_config(Config("your-sdk-key"))
ld_client = ldclient.get()

def track_metric(ld_client, user_id: str, metric_key: str, value: float, data: dict = None):
    """Track an event to a metric."""
    context = Context.builder(user_id).build()

    ld_client.track(
        metric_key,
        context,
        data=data,
        metric_value=value
    )

Common Tracking Patterns

def track_conversion(ld_client, user_id: str, amount: float, config_key: str):
    """Track a conversion event with revenue."""
    context = Context.builder(user_id).build()

    ld_client.track(
        "business.conversion",
        context,
        data={"configKey": config_key, "category": "electronics"},
        metric_value=amount
    )

def track_task_success(ld_client, user_id: str, task_type: str, success: bool):
    """Track task completion success/failure."""
    context = Context.builder(user_id).build()

    ld_client.track(
        "task.success_rate",
        context,
        data={"taskType": task_type},
        metric_value=1.0 if success else 0.0
    )

def track_satisfaction(ld_client, user_id: str, score: float, feedback_type: str):
    """Track user satisfaction (0-100 scale)."""
    context = Context.builder(user_id).build()

    ld_client.track(
        "user.satisfaction",
        context,
        data={"feedbackType": feedback_type},
        metric_value=score
    )

    # Track negative feedback separately for alerts
    if score < 50:
        ld_client.track(
            "user.negative_feedback",
            context,
            metric_value=1.0
        )

def track_revenue(ld_client, user_id: str, revenue: float, source: str):
    """Track revenue generated after agent interaction."""
    context = Context.builder(user_id).set("tier", "premium").build()

    if revenue > 0:
        ld_client.track(
            "revenue.impact",
            context,
            data={"source": source},
            metric_value=revenue
        )

3. Get Metrics (API)

Get Single Metric

def get_metric(project_key: str, metric_key: str):
    """Get a single metric definition."""
    API_TOKEN = os.environ.get("LAUNCHDARKLY_API_TOKEN")

    url = f"https://app.launchdarkly.com/api/v2/metrics/{project_key}/{metric_key}"

    headers = {"Authorization": API_TOKEN}

    response = requests.get(url, headers=headers)

    if response.status_code == 200:
        metric = response.json()
        print(f"[OK] Metric: {metric['key']}")
        print(f"     Name: {metric.get('name', 'N/A')}")
        print(f"     Kind: {metric.get('kind', 'N/A')}")
        print(f"     Numeric: {metric.get('isNumeric', False)}")
        print(f"     Event Key: {metric.get('eventKey', 'N/A')}")
        return metric
    elif response.status_code == 404:
        print(f"[INFO] Metric not found: {metric_key}")
        return None
    else:
        print(f"[ERROR] Failed to get metric: {response.status_code}")
        return None

List All Metrics

def list_metrics(project_key: str, limit: int = 20):
    """List all metrics in a project."""
    API_TOKEN = os.environ.get("LAUNCHDARKLY_API_TOKEN")

    url = f"https://app.launchdarkly.com/api/v2/metrics/{project_key}"

    headers = {"Authorization": API_TOKEN}
    params = {"limit": limit}

    response = requests.get(url, headers=headers, params=params)

    if response.status_code == 200:
        data = response.json()
        metrics = data.get("items", [])
        print(f"[OK] Found {len(metrics)} metrics:")
        for metric in metrics: