What is App Stack Builder?

App Stack Builder is a free AI-powered tool that helps founders and developers choose the right tech stack for their projects based on budget, app type, team size, and skill level.

What is the best tech stack for SaaS in 2026?

The best tech stack for SaaS in 2026 typically includes Next.js 16 for frontend, Supabase for database and auth, Vercel for hosting, Stripe for payments, and PostHog for analytics. App Stack Builder can generate a personalized recommendation based on your specific budget and requirements.

Is App Stack Builder free to use?

Yes, App Stack Builder is completely free to use. You can generate unlimited tech stack recommendations without any cost.

What types of apps can I build with the recommended stacks?

App Stack Builder supports various app types including SaaS applications, web apps, mobile apps, e-commerce stores, internal tools, and AI/ML products.

How much does a SaaS tech stack cost per month?

A modern SaaS tech stack can cost anywhere from $0-50/month for bootstrapped startups using free tiers, $100-300/month for growth-stage startups, to $500+/month for enterprise-ready infrastructure. App Stack Builder helps you find the best tools within your specific budget.

What is the best tech stack for solo founders?

For solo founders, we recommend Next.js + Vercel (free), Supabase (free tier), Supabase Auth (free), Stripe (pay as you go), and Plausible or PostHog for analytics. This stack can run your entire SaaS for under $50/month.

Can I export my tech stack recommendations?

Yes, you can export your tech stack recommendations as a PDF document or copy them to your clipboard. You can also share a link to your stack with others.

Agent Auth & Tool Calling

Best Agent Auth & Tool Calling Platforms in 2026

An agent that sends email, files tickets or updates a CRM needs to sign in to those apps as each of your users, keep their tokens fresh and never hand a password to the model. These platforms run that layer for you. Here are the leading options in 2026: two hosted platforms and two you can run yourself.

Agent Auth & Tool Calling Tools Compared

Tool	Pricing	Free tier
Composio	Free · paid from $29/mo
Arcade	Free · paid from $25/mo
Nango	Free · paid from $50/mo
ACI.dev	Free · then usage-based

The Best Agent Auth & Tool Calling Tools, Ranked

1. Composio

Free tier· Free · paid from $29/mo

Managed tool calling and OAuth for AI agents: 1,500+ app integrations, triggers and an MCP gateway, with a free tier of 100K tool calls a month.

Largest catalog: 1,500+ apps with managed OAuth
Generous free tier (100K tool calls)
SOC 2 Type II and ISO 27001

Composio & alternatives

2. Arcade

Free tier· Free · paid from $25/mo

MCP runtime that lets agents act as the signed-in user, with per-call authorization, policy hooks and 8,000+ permission-aware tools.

Per-call authorization scoped to user and agent
Policy hooks to block or redact without forking
Self-host in your VPC or air-gapped on Enterprise

Arcade & alternatives

3. Nango

Free tier· Free · paid from $50/mo

Source-available integration platform: managed OAuth for 1,000+ APIs, tool calls and an MCP server, syncs and webhooks. Free self-host for auth and proxy.

1,000+ APIs with managed OAuth
Syncs and webhooks as well as tool calls
Source on GitHub; free self-host for auth

Nango & alternatives

4. ACI.dev

Free tier· Free · then usage-based

Open-source (Apache-2.0) tool-calling platform: 600+ integrations, multi-tenant OAuth for end users, and a unified MCP server.

Apache-2.0: truly open source and self-hostable
Multi-tenant OAuth for end users built in
One MCP server for all tools

ACI.dev & alternatives

How to choose a agent auth & tool calling tool

Count the apps and the users. A few internal tools for your own team need far less than thousands of customers each connecting their own accounts.
Choose Composio for the widest catalog (1,500+ apps) and the largest free tier, 100,000 tool calls a month.
Choose Arcade when every call must be authorized against what both the user and the agent may do, or when it has to run in your VPC.
Choose Nango if the same integrations also need data syncs and webhooks. Its source is on GitHub under the Elastic License, and the free self-hosted build covers auth.
Choose ACI.dev for a fully open-source (Apache-2.0) platform you run yourself, after checking that the project is still active.

In-depth guideComposio vs Arcade (2026): Agent Auth & Tool Calling, Plus Open-Source Nango and ACI.devYour agent has to act inside Gmail, Slack and Salesforce as each of your users, without the model seeing a token. Composio and Arcade compared with Nango and ACI.dev on OAuth handling, licence and cost at 50 and 1,000 users.

Frequently Asked Questions

What are the best agent auth & tool calling tools for startups in 2026?⌄

The best agent auth & tool calling tools for startups in 2026 include Composio, Arcade, Nango, ACI.dev. Compare them by pricing, free tiers, and features in the list above.

What is the best free agent auth & tool calling tool?⌄

Free agent auth & tool calling options include Composio, Arcade, Nango, ACI.dev — all offer a free tier suitable for bootstrapped startups and MVPs.

How do I choose a agent auth & tool calling tool?⌄

Start with your budget and team size, prefer tools with a free tier to validate, and make sure your pick integrates with the rest of your stack. App Stack Builder can recommend a complete, budget-aware stack in about 60 seconds.

Need the whole stack, not just agent auth & tool calling?

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