The Agents Index

AI agent observability and evaluation tools

As of September 2026, none of these states a price. LangChain has a free plan.

Updated 18 September 20261 agent

Prices checked 18 September 2026

Reviewed by The Agents Index editorial team.

In A–Z order. How we rank →

This spot is open
Featured agents show here and on the home page.
- API access: Not stated
- Free tier: Not stated
- MCP server: Not stated
- Own API key: Not stated
- Open source: Not stated
- Self-hosted: Not stated
Get featured
LangChain
Open source agent frameworks plus LangSmith, a hosted platform to trace, evaluate, deploy and govern agents.
Free, then $39/seat/month
From
Free, then $39/seat/month
- API access: Yes
- Free tier: Yes
- MCP server: Yes
- Own API key: Partly
- Open source: Partly
- Self-hosted: Partly
Checked 18 September 2026
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Tools to trace, debug, test and evaluate what AI agents do, before and after they ship.

Questions buyers ask

Which agent here costs the least?

LangChain has a free plan.

When were these prices checked?

On 18 September 2026, each read on the maker's own pricing page.

Sources and method

Every price here was read on the agent maker's own pricing page.

LangChain: langchain.com/pricing, checked 18 September 2026