Kastor vs Relevance AI (2026)
A side-by-side comparison of Kastor and Relevance AI on pricing, features, and fit, so you can decide which is right for you.
Quick answer
Kastor and Relevance AI are both strong choices, but they fit different needs. Choose Kastor if you mainly need building multi-step research assistants that delegate subtasks to specialized sub-agents — its edge is completely free and open-source with no licensing fees or usage limits. Choose Relevance AI if you need automating b2b lead research and personalized outreach sequences — its edge is highly accessible no-code interface makes agent creation fast even for non-developers. Kastor starts at Free; Relevance AI starts at approximately $19/month for the Starter plan.
Features compared
- Multi-agent orchestration framework for coordinating multiple AI agents simultaneously
- Open-source codebase with full transparency and community-driven development
- Extensible architecture supporting custom LLM backends and tool integrations
- Agent communication and context-sharing protocols for collaborative task execution
- No-code AI agent builder with drag-and-drop workflow editor
- Multi-agent orchestration for complex, collaborative task automation
- Pre-built agent templates for sales, marketing, and operations use cases
- Integrations with 100+ business tools including HubSpot, Salesforce, and Slack
Pros & cons
- Completely free and open-source with no licensing fees or usage limits
- Gives developers full control over agent logic, memory, and integrations
- Active open-source community enables rapid iteration and community-contributed extensions
- Requires developer expertise to set up and configure compared to managed platforms
- Documentation and support may be limited compared to commercial multi-agent frameworks
- Highly accessible no-code interface makes agent creation fast even for non-developers
- Strong library of prebuilt templates accelerates time-to-value
- Flexible integrations allow agents to work within existing business tool stacks
- Usage credits on lower-tier plans can be consumed quickly on complex workflows
- Advanced customization and multi-agent setups may still require some technical understanding
The verdict
Choose Kastor if
you mainly need to building multi-step research assistants that delegate subtasks to specialized sub-agents. Its edge: completely free and open-source with no licensing fees or usage limits.
Choose Relevance AI if
you mainly need to automating b2b lead research and personalized outreach sequences. Its edge: highly accessible no-code interface makes agent creation fast even for non-developers.
Frequently asked questions
Is Kastor better than Relevance AI?
Neither is universally better. Kastor is stronger for building multi-step research assistants that delegate subtasks to specialized sub-agents, with an edge in completely free and open-source with no licensing fees or usage limits. Relevance AI is stronger for automating b2b lead research and personalized outreach sequences, with an edge in highly accessible no-code interface makes agent creation fast even for non-developers. Pick based on your main task.
Which is cheaper, Kastor or Relevance AI?
Kastor starts at Free and Relevance AI starts at approximately $19/month for the Starter plan. Free tier: Kastor — Fully free and open-source; Relevance AI — Free plan available with limited credits and agent runs per month.
What is Kastor best for?
Kastor is best for building multi-step research assistants that delegate subtasks to specialized sub-agents, automating complex workflows where multiple ai agents must collaborate and hand off results, prototyping agentic pipelines for startups or research teams without incurring api or platform costs.
What is Relevance AI best for?
Relevance AI is best for automating b2b lead research and personalized outreach sequences, enriching crm data by having agents browse the web and extract information, handling customer support inquiries with ai agents that escalate when needed.
Do Kastor and Relevance AI have free plans?
Kastor: Fully free and open-source. Relevance AI: Free plan available with limited credits and agent runs per month. Check each tool's pricing page for current limits, as plans change.