21st Agents SDK vs Mastra: Which Should You Choose in 2026?
Choosing between 21st Agents SDK and Mastra comes down to understanding what each tool does best. This comparison breaks down the key differences so you can make an informed decision based on your specific needs, not marketing claims.
By Toolradar Team · Last updated May 6, 2026 · Methodology
Short on time? Here's the quick answer
We've tested both tools. Here's who should pick what:
21st Agents SDK
The fastest way to integrate AI agents with built-in UI and essential features into your applications.
Best for you if:
- 0
- • You need ai coding features specifically
- • Quickly integrate AI agents into applications.
- • Includes built-in UI, chat history, and spend limits.
Mastra
Build AI-powered applications and agents with a modern TypeScript stack.
Best for you if:
- 0
- • You want to try before committing
- • You need ai agents features specifically
- • Framework for building AI apps and agents with TypeScript.
- • Integrates with 40+ AI providers and supports autonomous agents and workflows.
| At a Glance |  21st Agents SDK |  Mastra |
|---|---|---|
Price | Paid | Free + Paid |
Best For | AI Coding | AI Agents |
Rating | — | — |
| Feature | 21st Agents SDK | Mastra |
|---|---|---|
| Pricing Model | Paid | Freemium |
| Community Rating | No ratings yet | No ratings yet |
| Total Reviews | 0 | 0 |
| Community Upvotes | 100 | 202 |
| Categories | AI CodingAI Agents | AI AgentsAI Model Deployment |
How 21st Agents SDK and Mastra Compare
21st Agents SDK
The fastest way to integrate AI agents with built-in UI and essential features into your applications.
Paid
Mastra
Build AI-powered applications and agents with a modern TypeScript stack.
Free tier available
21st Agents SDK is a ai coding tool. Mastra is in ai agents.
Who Should Use What?
On a budget?
Mastra has a free tier. 21st Agents SDK is paid only.
Go with: Mastra
Want the highest-rated option?
Neither has user reviews yet.
Go with: 21st Agents SDK
Value user reviews?
Neither has user reviews yet.
Go with: Mastra
3 Questions to Help You Decide
What's your budget?
21st Agents SDK is paid. Mastra is freemium. Mastra lets you start free.
What's your use case?
21st Agents SDK is a ai coding tool. Mastra is in ai agents. Pick the category that matches your needs.
How important are ratings?
Neither has user reviews yet.
Key Takeaways
Mastra
- 0
- More community upvotes (202)
- Free tier available
- Our pick for this comparison
21st Agents SDK
- Better fit for ai coding
The Bottom Line
Mastra is our pick.
Frequently Asked Questions
Is 21st Agents SDK or Mastra better?
Mastra is rated high in our evaluation. 21st Agents SDK is paid and Mastra is freemium.
What are 21st Agents SDK and Mastra used for?
21st Agents SDK: The fastest way to integrate AI agents with built-in UI and essential features into your applications.. Mastra: Build AI-powered applications and agents with a modern TypeScript stack..
What does 21st Agents SDK cost vs Mastra?
21st Agents SDK is a paid tool. Mastra is freemium (free tier + paid plans). Visit their websites for detailed pricing.