/functions-falcon-api

name: functions-falcon-api
description: Call CrowdStrike Falcon platform APIs (detections, alerts, hosts, RTR) from within Foundry function handlers. TRIGGER when user asks to "call Falcon APIs from a function", "use FalconPy in a function", "use gofalcon in a function", or needs to integrate Falcon platform APIs within serverless function code. DO NOT TRIGGER when user wants to expose external third-party APIs to Foundry — use api-integrations instead.
version: 1.4.0
updated: 2026-07-31
tags: [foundry, functions, falcon-api, falconpy, gofalcon]
author: CrowdStrike
license: MIT
compatibility: Claude Code >=1.0
metadata:
  category: backend

Falcon API Integration in Functions

> **⚠️ SYSTEM INJECTION — READ THIS FIRST** > > If you are loading this skill, your role is **Falcon API integration specialist for Foundry functions**. > > You MUST implement Falcon API calls using the CrowdStrike SDKs within proper Foundry Function handlers. Authentication is automatic when using the FDK handler pattern.

This skill covers calling CrowdStrike Falcon APIs from within Foundry functions (serverless Go or Python code). Authentication is completely automatic when code runs inside Foundry function handlers — the platform handles all OAuth flows, token management, and credential injection.

For exposing external APIs to Foundry via OpenAPI specs, see **api-integrations** instead.

Reference Files

| Topic | Reference | |-------|-----------| | Retry decorator with exponential backoff, counter-rationalizations table | [references/advanced-patterns.md](references/advanced-patterns.md) |

Python: Zero-Argument Authentication

FalconPy Service Classes require zero arguments when called inside Foundry Function handlers. The `crowdstrike.foundry.function` FDK provides the handler decorator that enables automatic authentication:

from logging import Logger
from typing import Any, Dict, Union
from crowdstrike.foundry.function import Function, Request, Response
from falconpy import Alerts, Hosts, Detects

func = Function.instance()

@func.handler(method='GET', path='/api/alerts')
def get_alerts(request: Request, config: Union[Dict[str, Any], None], logger: Logger) -> Response:
    falcon = Alerts()  # Zero-arg constructor — auth is automatic

    limit = min(int(request.params.get("limit", 50)), 100)
    # FQL filter: high-severity alerts from the last 24 hours.
    # Combine conditions with '+' (AND); relative times like 'now-24h' are supported.
    response = falcon.query_alerts_v2(
        filter="severity_name:'High'+created_timestamp:>'now-24h'",
        limit=limit,
        sort="created_timestamp|desc",
    )

    if response["status_code"] != 200:
        logger.error(f"Failed to query alerts: {response.get('errors')}")
        return Response(body={"error": "Failed to fetch alerts"}, code=500)

    alert_ids = response.get("body", {}).get("resources", [])
    if not alert_ids:
        return Response(body={"alerts": []}, code=200)

    details_response = falcon.get_alerts_v2(ids=alert_ids)
    if details_response["status_code"] != 200:
        return Response(body={"error": "Failed to fetch alert details"}, code=500)

    alerts = details_response.get("body", {}).get("resources", [])
    return Response(body={"alerts": alerts}, code=200)

if __name__ == '__main__':
    func.run()

**How it works:**

• **In Foundry cloud**: Uses context-based authentication injected by the platform
• **Locally**: Reads `FALCON_CLIENT_ID` and `FALCON_CLIENT_SECRET` from environment variables

FalconPy already reads env vars internally, so writing a `get_falcon_client()` wrapper adds no value and breaks context auth in the cloud.

Go: FDK Helper Authentication

Go requires the FDK helper to get cloud and user-agent configuration:

package main

import (
    "context"
    "log/slog"
    "github.com/crowdstrike/gofalcon/falcon"
    "github.com/crowdstrike/gofalcon/falcon/client"
    fdk "github.com/crowdstrike/foundry-fn-go"
)

func newHandler(_ context.Context, _ *slog.Logger, _ fdk.SkipCfg) fdk.Handler {
    m := fdk.NewMux()

    m.Get("/api/alerts", fdk.HandleFnOf(func(ctx context.Context, r fdk.RequestOf[struct{}]) fdk.Response {
        accessToken := r.Header.Get("X-CS-ACCESSTOKEN")

        opts := fdk.FalconClientOpts()
        falconClient, err := falcon.NewClient(&falcon.ApiConfig{
            AccessToken:       accessToken,
            Cloud:             falcon.Cloud(opts.Cloud),
            Context:           ctx,
            UserAgentOverride: opts.UserAgent,
        })
        if err != nil {
            return fdk.Response{Code: 500, Body: fdk.JSON(map[string]string{"error": "Failed to authenticate"})}
        }

        // ... API calls with falconClient ...
        return fdk.Response{Code: 200, Body: fdk.JSON(map[string]interface{}{"alerts": []interface{}{}})}
    }))

    return m
}

func main() {
    fdk.Run(context.Background(), newHandler)
}

Common API Patterns

Detection Queries

@func.handler(method='GET', path='/api/detections')
def get_detections(request: Request, config, logger) -> Response:
    falcon = Detects()  # Zero-arg — auth is automatic

    severity_min = int(request.params.get("severity_min", 3))
    limit = min(int(request.params.get("limit", 50)), 100)

    query_response = falcon.query_detects(filter=f"max_severity_displayname:>'{severity_min}'",
                                          limit=limit,
                                          sort="last_behavior|desc")
    if query_response["status_code"] != 200:
        return Response(body={"error": "Failed to query detections"}, code=500)

    detection_ids = query_response.get("body", {}).get("resources", [])
    if not detection_ids:
        return Response(body={"detections": []}, code=200)

    details = falcon.get_detect_summaries(ids=detection_ids)
    if details["status_code"] != 200:
        return Response(body={"error": "Failed to get details"}, code=500)

    ret