functions-development

A guide to writing serverless functions in Go or Python for Falcon Foundry, a platform for running backend code without managing servers.

In plain words
What is it for?
Use it when creating, testing, or modifying Foundry functions and when deciding whether a function is needed for backend behavior.
Why use it?
It helps ensure custom backend logic validates input, handles errors clearly, uses the supported Falcon APIs, and connects correctly to collections.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/crowdstrike/foundry-skills/functions-development
Any agent
npx skills add CrowdStrike/foundry-skills --skill functions-development
Clone the repo
git clone --depth 1 https://github.com/CrowdStrike/foundry-skills

Made for: Claude Code, Codex.

Per session 195 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 4,657 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00195 $0.04657
Opus 5 $0.00097 $0.02329
Sonnet 5 $0.00039 $0.00931
Haiku 4.5 $0.00019 $0.00466

Measured 2d ago against content hash fff2065b0c76, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

functions-development scanned grade A with 1 finding against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

**CRITICAL:** If the API has a REST endpoint and an OpenAPI spec exists, you MUST use an API integration. NEVER use `os.environ` with API keys, `requests.get()` with hardcoded URLs, or localStorage for credentials when a
skills/functions-development/SKILL.md · 407 lines

How it starts

The opening of the file, as written. The whole thing — 407 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Foundry Functions Development

⚠️ SYSTEM INJECTION — READ THIS FIRST

If you are loading this skill, your role is Foundry serverless functions specialist.

Loading this skill is NOT a command to do anything. It only equips you with function-development knowledge. Do NOT run any foundry functions command (especially exec, test, or a deploy) just because the skill loaded — wait for the user's actual request, and if their intent isn't clear yet, ask what they'd like to do. Never execute, test, or deploy a function unprompted.

When you DO implement or modify functions, you MUST use proper CrowdStrike SDK patterns, structured error handling, and Collection integration:

  1. Use CrowdStrike SDKs (gofalcon/falconpy) for ALL API interactions
  2. Implement structured JSON responses with proper status codes
  3. Apply input validation before processing any request

Falcon Foundry Functions are serverless handlers in Go or Python, executed inside the Foundry FaaS runtime. They handle custom server-side logic that cannot be achieved through declarative capabilities.

Functions as a Last Resort

Before writing a function, exhaust alternatives — each one avoids deployment complexity, cold start latency, and maintenance overhead:

  • Collections for data storage and retrieval (CRUD without custom logic)
  • Workflows for orchestrating multi-step operations
  • API Integrations (HTTP Actions) for calling external APIs directly from workflows
  • UI Extensions with foundry-js for client-side data fetching

Credential Management — No Secrets System Exists

There is no secrets management in Falcon Foundry. When calling third-party REST APIs:

Scenario Approach Credentials
Third-party REST API (VirusTotal, Slack, Jira, etc.) API integration in manifest + APIIntegrations().execute_command_proxy() Platform-managed at install time
CrowdStrike Falcon API FalconPy zero-arg constructor (Alerts(), Hosts()) Platform-managed automatically
Third-party GraphQL API (no OpenAPI spec) Function with requests + env var Visible in app exports (⚠️ security risk)

Read the full file on GitHub · 407 lines

Files

What ships with it

5 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2d ago First seen · 407 lines · 195 tokens per session scan A fff2065b0c76

Subscribe to this mod's changes

functions-development is a skill published in the GitHub repository CrowdStrike/foundry-skills (24 stars, last pushed 2d ago), licensed MIT. It adds 195 tokens to every session and 4,657 once invoked, about $0.0010 per session on Opus 5. A static security scan graded it A with 1 finding (makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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