---
name: apilookup
description: "Use when work depends on current external API behavior, SDK docs, framework versions, breaking changes, migration guides, changelogs, release notes, deprecations, or syntax that may have changed."
---

# API Lookup Skill

Look up API documentation, SDK references, library versions, and migration guides using a three-tier resolution strategy that starts with local Flow skill references and escalates to targeted web searches only when needed.

## Overview

Three tiers of resolution, applied in order:

1. **Local skill references** — if a matching Flow skill exists and the registry entry is fresh (< 30 days), load the skill's curated `references/` docs directly. No network needed.
2. **Targeted web lookup** — if local refs are stale (> 30 days) or the query needs more, use the registry's known URLs for targeted searches (max 2-4).
3. **Arbitrary lookup** — for technologies without a matching skill, broad web search with a version-first strategy (max 2-4 searches).

## Usage Patterns

Example queries this skill handles:

- "What's the latest Litestar version and what changed?"
- "How do I use React Server Components?"
- "Show me the SQLAlchemy 2.0 migration guide"
- "What breaking changes are in Angular 19?"
- "What's the current Go module proxy API?" (arbitrary — no local skill)
- "Check if there's a newer version of Tailwind CSS"

<workflow>

## How It Works

### Version Registry

`references/registry.json` maps every Flow skill to:

- Current known version and last-checked date
- Package registry (PyPI, npm, crates.io, etc.)
- Official docs URL, changelog URL, and GitHub repo
- Search hint keywords for targeted queries

### Staleness Thresholds

| Age of registry entry | Action |
|-----------------------|--------|
| < 30 days | Trust local skill references, answer directly |
| 30-90 days | Use local refs as baseline, verify version via web |
| > 90 days | Treat as potentially outdated, do full version check |

### Search Budget

All web lookups are capped at **2-4 searches max**. Prefer `WebFetch` on known URLs over `WebSearch` when registry URLs are available — it is faster and more precise.

</workflow>

<guardrails>

## Lookup Rules

See `references/lookup-strategy.md` for the full decision tree. Key principles:

1. **Always start local** — check the registry and load matching skill refs if fresh
2. **Be targeted** — use registry URLs and package names for precise queries
3. **Respect the budget** — 2-4 searches max, stop once you have an authoritative answer
4. **Cite sources** — always include links to official docs or changelogs
5. **Note version gaps** — if local refs cover version X but the current release is Y, tell the user explicitly

</guardrails>

## References Index

- **[Lookup Strategy](references/lookup-strategy.md)** — Detailed three-tier resolution instructions
- **[Version Registry](references/registry.json)** — Package metadata and staleness tracking for all skills
- **[Registry Schema](references/registry-schema.md)** — Documents the registry JSON format and fields

<validation>

## Validation Checkpoint

Before delivering an answer based on an API lookup, verify:

- [ ] **Staleness check** was performed against `registry.json` for known skills
- [ ] **Tier 1 (Local)** was tried first for fresh entries (< 30 days)
- [ ] **Tier 2 (Targeted)** was used for stale entries, capping at 2-4 searches
- [ ] **Tier 3 (Arbitrary)** used for unknown tech, anchoring on today's date
- [ ] **Citations** are included with direct links to official docs or changelogs
- [ ] **Version gaps** between local refs and current docs are explicitly noted

</validation>

<example>

## Example: Looking up React Server Components

**Query:** "How do I use React Server Components in Next.js?"

1. **Identify Tech:** React, Next.js.
2. **Check Registry:** Matches `react` skill. `last_checked` is 45 days ago (Tier 2).
3. **Execute Tier 2:**
   - **Step 1 (Version):** WebFetch `https://github.com/facebook/react/releases` -> React 19 is latest.
   - **Step 2 (Specific):** WebSearch `site:nextjs.org react server components pattern 2026`.
4. **Synthesize:**
   - "Based on Next.js 15+ documentation (compatible with React 19):"
   - Explain `use client` vs default server components.
   - Provide code example of a Server Component fetching data.
   - **Citations:** [Next.js RSC Docs](https://nextjs.org/docs/app/building-your-application/rendering/server-components), [React 19 Upgrade Guide](https://react.dev/blog/2024/12/05/react-19).

</example>