Mastra vs Vertex AI Agent Builder

as AI assistants see them, week of 2026-09-14

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Mastra and Vertex AI Agent Builder both sit near the bottom of the pack, with overall scores of 8 and 9 out of 100. Mastra is named in 12 of 71 answers, Vertex AI Agent Builder in 14 of 71. Mastra does best on "Which AI agent framework should a developer choose?" and "What's the best tool for building multi-agent systems?" (2 of 3 answers each), while Vertex AI Agent Builder is named in every answer (4 of 4) for "What are the best platforms for building AI agents?" Head-to-head, they're evenly matched: each wins 4 questions outright, with 12 ties. Neither is ever mentioned for voice agents, non-technical founders, or self-hosted setups.

Head to head

metric	Mastra	Vertex AI Agent Builder
score	8	9
questions won	9	8

By assistant

Mastra

assistant	score	named in, this week	usual spot, this week
ChatGPT	5	10% of answers	#6.5
Claude	18	40% of answers	#9.1
Gemini	0	0% of answers
Perplexity	7	11% of answers	#4.5

Vertex AI Agent Builder

assistant	score	named in, this week	usual spot, this week
ChatGPT	15	25% of answers	#5.2
Claude	10	25% of answers	#14.4
Gemini	7	17% of answers	#10.5
Perplexity	6	11% of answers	#7.0

Where they differ

Only Mastra gets named for

What are the best open-source AI agent frameworks?
What's the best tool to build an AI agent that browses the web and does research?
What's the best platform to build and deploy AI agents for a startup?

Only Vertex AI Agent Builder gets named for

What's the best platform to build an AI agent that connects to my company's data?
What's the best no-code tool to build an AI agent?

More comparisons

Not sold on either?

Scores count how often each assistant names a product, weighted by position. How the score works · Full AI agent builders leaderboard