Build with Firestore NoSQL database - real-time sync, offline support, and scalable document storage. Use when: creating collections, querying documents, setting up security rules, handling real-time listeners, or troubleshooting permission-denied, quota exceeded, invalid query, or offline persistence errors. Prevents 10 documented errors.

Build with Firebase Authentication - email/password, OAuth providers, phone auth, and custom tokens. Use when: setting up auth flows, implementing sign-in/sign-up, managing user sessions, protecting routes, or troubleshooting auth/invalid-credential, auth/popup-closed, auth/user-not-found, or token refresh errors. Prevents 12 documented errors.

Generate custom favicons from logos, text, or brand colors - prevents launching with CMS defaults. Extract icons from logos, create monogram favicons from initials, or use branded shapes. Outputs all required formats: favicon.svg, favicon.ico, apple-touch-icon.png, and web app manifest. Use when: initializing new websites, replacing WordPress/CMS default favicons, converting logos to favicons, creating branded icons from text only, or troubleshooting favicon not displaying, iOS icon transparency, or missing manifest files.

Build MCP servers in Python with FastMCP to expose tools, resources, and prompts to LLMs. Supports storage backends, middleware, OAuth Proxy, OpenAPI integration, and FastMCP Cloud deployment. Prevents 30+ errors. Use when: creating MCP servers, or troubleshooting module-level server, storage, lifespan, middleware, OAuth, background tasks, or FastAPI mount errors.

Build Python APIs with FastAPI, Pydantic v2, and SQLAlchemy 2.0 async. Covers project structure, JWT auth, validation, and database integration with uv package manager. Prevents 7 documented errors. Use when: creating Python APIs, implementing JWT auth, or troubleshooting 422 validation, CORS, async blocking, form data, background tasks, or OpenAPI schema errors.

Multi-provider email sending for Cloudflare Workers and Node.js applications. Build transactional email systems with Resend (React Email support), SendGrid (enterprise scale), Mailgun (developer webhooks), or SMTP2Go (reliable relay). Includes template patterns, webhook verification, attachment handling, and error recovery. Use when sending emails via API, handling bounces/complaints, or migrating between providers.

Build conversational AI voice agents with ElevenLabs Platform. Configure agents, tools, RAG knowledge bases, agent versioning with A/B testing, and MCP security. React, React Native, or Swift SDKs. Prevents 34 documented errors. Use when: building voice agents, AI phone systems, agent versioning/branching, MCP security, or troubleshooting @11labs deprecated, webhook errors, CSP violations, localhost allowlist, tool parsing errors.

Build type-safe D1 databases with Drizzle ORM. Includes schema definition, migrations with Drizzle Kit, relations, and D1 batch API patterns. Prevents 18 errors including SQL BEGIN failures, cascade data loss, 100-parameter limits, and foreign key issues. Use when: defining D1 schemas, managing migrations, bulk inserts, or troubleshooting D1_ERROR, BEGIN TRANSACTION, foreign keys, "too many SQL variables".

Four slash commands for documentation lifecycle: /docs, /docs-init, /docs-update, /docs-claude. Create, maintain, and audit CLAUDE.md, README.md, and docs/ structure with smart templates. Use when: starting new projects, maintaining documentation, auditing docs for staleness, or ensuring CLAUDE.md matches project state.

Deploy Django on Google App Engine Standard with Cloud SQL PostgreSQL. Covers Unix socket connections, Cloud SQL Auth Proxy for local dev, Gunicorn configuration, and production-ready settings. Use when: deploying Django to App Engine, configuring Cloud SQL PostgreSQL, setting up Unix socket connections, or troubleshooting "No such file or directory", "connection refused", or "FATAL: password authentication failed".

Generate complete, accessible color palettes from a single brand hex. Creates 11-shade scale (50-950), semantic tokens (background, foreground, card, muted), and dark mode variants. Includes WCAG contrast checking for text accessibility. Use when: setting up design system, creating Tailwind theme, building brand colors from single hex, converting designs to code, checking color accessibility.

Build durable workflows with Cloudflare Workflows (GA April 2025). Features step.do, step.sleep, waitForEvent, Vitest testing, automatic retries, and state persistence for long-running tasks. Prevents 12 documented errors. Use when: creating workflows, implementing retries, or troubleshooting NonRetryableError, I/O context, serialization errors, waitForEvent timeouts, getPlatformProxy failures.

Run LLMs and AI models on Cloudflare's GPU network with Workers AI. Includes Llama 4, Gemma 3, Mistral 3.1, Flux images, BGE embeddings, streaming, and AI Gateway. Handles 2025 breaking changes. Prevents 7 documented errors. Use when: implementing LLM inference, images, RAG, or troubleshooting AI_ERROR, rate limits, max_tokens, BGE pooling, context window, neuron billing, Miniflare AI binding, NSFW filter, num_steps.

Set up Cloudflare Workers with Hono routing, Vite plugin, and Static Assets. Prevents 10 errors including export syntax, routing conflicts, Vite 8 nodejs_compat, base option regression, and cache corruption. Use when: creating Workers projects, configuring Hono/Vite, or troubleshooting export syntax, API route conflicts, HMR issues, or Vite 8+ compatibility.

Build semantic search with Cloudflare Vectorize V2. Covers async mutations, 5M vectors/index, 31ms latency, returnMetadata enum changes, and V1 deprecation. Prevents 14 errors including dimension mismatches, TypeScript types, testing setup. Use when: building RAG or semantic search, troubleshooting returnMetadata, V2 timing, metadata index, dimension errors, vitest setup, or wrangler --json output.

Add bot protection with Turnstile (CAPTCHA alternative). Use when: protecting forms, securing login/signup, preventing spam, migrating from reCAPTCHA, integrating with React/Next.js/Hono, implementing E2E tests, or debugging CSP errors, token validation failures, Chrome/Edge first-load issues, multiple widget rendering bugs, timeout-or-duplicate errors, or error codes 100*/106010/300*/600*.

Build async message queues with Cloudflare Queues for background processing. Use when: handling async tasks, batch processing, implementing retries, configuring dead letter queues, managing consumer concurrency, or troubleshooting queue timeout, batch retry, message loss, or throughput exceeded. Prevents 13 documented errors including multi-dev limitations, remote binding conflicts, and DLQ issues.

Build Python APIs on Cloudflare Workers using pywrangler CLI and WorkerEntrypoint class pattern. Includes Python Workflows for multi-step DAG automation. Prevents 11 documented errors. Use when: building Python serverless APIs, migrating Python to edge, or troubleshooting async errors, package compatibility, handler pattern mistakes, RPC communication issues.

Store key-value data globally with Cloudflare KV's edge network. Use when: caching API responses, storing configuration, managing user preferences, handling TTL expiration, or troubleshooting KV_ERROR, 429 rate limits, eventual consistency, cacheTtl errors, wrangler types issues, or remote binding configuration.

Store and transform images with Cloudflare Images API and transformations. Use when: uploading images, implementing direct creator uploads, creating variants, generating signed URLs, optimizing formats (WebP/AVIF), transforming via Workers, or debugging CORS, multipart, AVIF limits, metadata stripping, cache issues, or error codes 9401-9413.