Comparison
Best AI agent evaluation tools in 2026
There is no single best among AI agent evaluation tools. They check tool calls, trajectories, and whether a job still finishes. Promptfoo, DeepEval, Inspect, and Pydantic Evals are libraries you run locally or in CI. LangSmith, Langfuse, Braintrust, and Confident AI add hosted tracing and online evals. Phoenix is source-available under Elastic License 2.0 for self-hosting. This page does not invent a ranking.
Last verified November 8, 2026. Cells are licence, list price, and platform from official pages. This is not a quality ranking.
Key takeaways
- Evaluation is not the same as observability. Tracing tells you what happened. An eval scores a step or a whole job against a written expectation.
- Open-source libraries and hosted platforms often pair: DeepEval with Confident AI, Pydantic Evals with Logfire, LangChain libraries with LangSmith, Phoenix with Arize AX.
- A behavioral eval checks one action. An end-to-end benchmark still answers whether the job finished. Keep both.
Last verified November 2026
Which AI agent evaluation tool is best in 2026?
There is no single best among AI agent evaluation tools. Pick a tool for the check you need to keep running. Promptfoo, DeepEval, Inspect, and Pydantic Evals are libraries you run locally or in CI. LangSmith, Langfuse, Braintrust, and Confident AI add hosted tracing and online evals. Phoenix is source-available under Elastic License 2.0 for self-hosting. This page does not invent a ranking.
A behavioral evaluation checks one action you can point at in a run. An end-to-end benchmark still answers whether the job finished. The working guide is How do you evaluate an AI agent harness? Official SWE-bench and Terminal-Bench rows stay on the November 2026 harness benchmark. The shelf for this table is Best AI agents.
Which open source AI agent evaluation tools can you run in CI?
Promptfoo, Inspect, and Pydantic Evals are MIT; DeepEval is Apache licensed on PyPI; Langfuse’s core is MIT except ee/ folders. Self-hosting Langfuse’s core is free on its pricing page. Phoenix uses Elastic License 2.0: you may run it yourself, and you may not offer it to third parties as a hosted or managed service.
Inspect is the row that documents sandboxed agent evals and the ability to drive Claude Code, Codex CLI, or Gemini CLI as an external agent. DeepEval documents trajectory-based evaluation and agent metrics such as tool correctness. Pydantic Evals documents grading the sequence and arguments of tool calls, including against a sample of live traffic. Promptfoo documents local evaluation and CI, with a 10,000-probe monthly cap on Community red teaming.
LangSmith, Braintrust, and Confident AI are hosted platforms. They belong on this page because teams often compare them with the libraries above. They are not OSI-licensed runtimes. The harnesses those tests wrap are compared in Best AI agent harness.
How do AI agent evaluation tools compare on price and licence?
The table lists 8 evaluation tools with a Best for label, open-source licence, list price, and local, CI, or hosted platform from official pages, last verified November 2026.
Sort any column. A blank would mean the official page did not state the fact. Source numbers match the list at the end of the page. Last verified November 8, 2026. The shelf for this table is Best AI agents.
- Promptfoo
- DeepEval
- Inspect
- Pydantic Evals
- LangSmith
- Langfuse
- Braintrust
- Arize Phoenix
| Arize Phoenix | Arize AI | Best for self-hosted source-available evals | Elastic License 2.0 (source-available; you may not offer it as a hosted or managed service) | No Cloud price on the Phoenix docs page checked 8 Nov 2026. You can self-host. Arize AX is the separate managed platform. | Self-host. Tracing over OpenTelemetry. Python, TypeScript, and Java instrumentation is documented. | [15] [16] |
| Braintrust | Braintrust | Best for hosted experiments | Hosted platform (open-source SDKs are separate; this row is the product page) | Starter $0/month with $10 model credits, 1 GB processed data, 10k scores, 14-day retention. Pro $249/month with $100 credits, 5 GB, 50k scores, 30-day retention. Enterprise custom. Read 8 Nov 2026. | Hosted. Enterprise lists on-prem or hosted deployment. | [14] |
| DeepEval | Confident AI | Best for pytest-style agent metrics | Apache Software License (PyPI classifier) | The library has no licence fee. Confident AI Free is $0 with 2 seats, 1 project, 5 test runs a week, and 1 GB-month of traces. Starter is $200/month per organization. Team is $2,000/month. Enterprise is custom. Read 8 Nov 2026. | Python (and a TypeScript SDK in beta, per DeepEval’s own blog). Unit tests in CI. Optional Confident AI cloud. | [3] [4] |
| Inspect | UK AI Security Institute and Meridian Labs | Best for sandboxed agent evals | MIT | No hosted product price. pip install inspect-ai. You pay the model provider you call. | Python CLI and API. VS Code extension. Sandboxes: Docker, Kubernetes, Modal, Proxmox, Vagrant, and others. Local inference via Hugging Face, vLLM, or SGLang is documented. | [5] [6] |
| Langfuse | Langfuse (ClickHouse) | Best for self-hosted tracing | MIT for code outside ee/ directories; ee/ code is separately licensed | Self-host the open-source core for free. Cloud Hobby is free (50k units/month, 2 users). Core $29/month. Pro $199/month. Enterprise $2,499/month. Extra Cloud units start at $8 per 100k. Read 8 Nov 2026. | Cloud (US, EU, or Japan) or self-host with Docker Compose or Kubernetes. | [12] [13] |
| LangSmith | LangChain | Best for hosted traces and evals | Hosted platform; LangChain libraries are open source | Developer $0/seat then pay as you go, 5,000 base traces/month. Plus $39/seat, 10,000 base traces/month. Enterprise custom, including self-hosted and hybrid. 1 LSU = $1. Read 8 Nov 2026. | LangChain Cloud (US or EU). Enterprise adds hybrid and self-hosted. | [10] [11] |
| Promptfoo | Promptfoo | Best for local CI and red teaming | MIT | Community is free forever, including local or self-hosted runs. Red teaming on Community is up to 10,000 probes a month. Enterprise and On-Premise are custom. Read 8 Nov 2026. | Local CLI, self-host, CI/CD. Cloud and on-premise are Enterprise options. | [1] [2] |
| Pydantic Evals | Pydantic | Best for typed Python evals | MIT (pydantic-ai repository) | pip install pydantic-evals. Optional Logfire: Personal free with 10 million records a month; Team $49/mo; Growth $249/mo. Checked 3 Nov 2026 for Logfire. | Python, code-first datasets and evaluators. Results in the terminal, on disk, or in Logfire. | [7] [8] [9] |
Which AI agent evaluation tool is best for each check?
Promptfoo fits local CI gates; DeepEval fits pytest-style agent metrics; Inspect fits sandboxed agent evals; Langfuse and Phoenix fit self-hosted tracing plus evals.
These are job-fit notes from the documented scope, not scores.
Best for CI and red-team prompt tests
Promptfoo’s Community plan is free, MIT licensed, and documents local or self-hosted runs plus CI. Red teaming on Community is capped at 10,000 probes a month. Enterprise is custom.
Best for pytest-style agent metrics
DeepEval is Apache licensed on PyPI and documents trajectory-based evaluation and agent metrics such as tool correctness. Confident AI is the hosted companion, with a free tier and Starter at $200 a month.
Best for sandboxed agent evals
Inspect, from the UK AI Security Institute and Meridian Labs, is MIT licensed. It documents built-in agents, external agents such as Claude Code and Codex CLI, and sandboxes including Docker, Kubernetes, and Modal.
Best self-hostable tracing plus evals
Langfuse’s core is MIT except for ee/ directories. Cloud Hobby is free with 50,000 units a month; Core is $29 a month. Phoenix is Elastic License 2.0: you may run it yourself, and you may not offer it as a hosted service.
How was this AI agent evaluation comparison checked?
Every cell comes from an official product page, a licence file, or a listing on this site that already cites that official page.
Prices are list prices with the billing unit the vendor printed. Licences are the SPDX or file name on the repository, not a guess. This page does not invent ratings, traffic, or a composite score, and it does not treat benchmark percentages from different tasks as one experiment.
What else do people ask about AI agent evaluation tools?
These short answers cover open source, hosted platforms, cost, and how a behavioral eval differs from a benchmark.
What is an AI agent evaluation tool?
It is software that scores an agent against a written expectation. That can be one tool call, a whole trajectory, or whether a frozen set of tasks still finishes. Tracing without a score is observability, not evaluation.
What is the best open source AI agent evaluation tool?
Promptfoo, Inspect, and Pydantic Evals are MIT. DeepEval is Apache licensed on PyPI. Langfuse’s core is MIT except for ee/ folders. Phoenix is Elastic License 2.0, which is source-available and forbids offering it as a hosted service. Which one fits depends on whether you need CI gates, sandboxes, or production traces.
How is a behavioral eval different from a benchmark?
A behavioral eval checks one observable action, such as a tool call or a clarifying question. A benchmark scores a frozen set of tasks. Google’s 9 September 2026 harness-engineering post treats the benchmark as the destination and the behavioral eval as the check you use while you change the harness.
Do I need a hosted platform?
Not to start. Promptfoo, DeepEval, Inspect, and Pydantic Evals run in your own process or CI. Hosted platforms add shared traces, annotation queues, and online evals on live traffic. Several open-source tools have an optional paid companion.
How much do AI agent evaluation tools cost?
Open-source libraries are free to install. You still pay the model used as a judge, if any. LangSmith starts at $0 a seat then pay as you go, with Plus at $39 a seat. Langfuse Cloud has a free Hobby tier and paid Core, Pro, and Enterprise plans. Braintrust’s Starter plan is $0 a month with included credits; Pro is $249 a month. Confident AI is the hosted companion to DeepEval. Figures are list prices read in November 2026.
Is Phoenix open source?
Phoenix’s repository uses Elastic License 2.0. You may run it yourself. You may not provide it to third parties as a hosted or managed service. That is not an OSI open-source licence. Langfuse’s non-ee code is MIT.
Why are there no benchmark percentages on this page?
Those numbers belong on a dated leaderboard with the harness that produced them. Mixing scores from different tasks or versions as if they were one experiment would be misleading. The November 2026 harness benchmark copies official SWE-bench and Terminal-Bench rows instead.
Sources
- 1Promptfoo pricing (read 8 Nov 2026)
- 2promptfoo/promptfoo LICENSE (MIT)
- 3DeepEval docs (read 8 Nov 2026)
- 4Confident AI pricing (read 8 Nov 2026)
- 5Inspect, UK AI Security Institute (read 8 Nov 2026)
- 6inspect_ai LICENSE (MIT)
- 7Pydantic Evals
- 8pydantic-ai LICENSE (MIT)
- 9This site, Pydantic AI listing (checked 3 Nov 2026)
- 10LangChain, LangSmith pricing (read 8 Nov 2026)
- 11This site, LangChain listing (checked 3 Nov 2026)
- 12Langfuse pricing (read 8 Nov 2026)
- 13langfuse LICENSE (MIT except ee/)
- 14Braintrust pricing (read 8 Nov 2026)
- 15Arize Phoenix docs (read 8 Nov 2026)
- 16Arize Phoenix LICENSE (Elastic License 2.0)
Cite or embed this
The citation names this page and the date above. The embed is a blockquote with a link back here.
Citation
AI Agents Info. "Best AI agent evaluation tools." Last verified November 2026. https://www.aiagentsinfo.com/best/ai-agent-evaluation-tools.
Embed
<blockquote cite="https://www.aiagentsinfo.com/best/ai-agent-evaluation-tools"> <p>There is no single best among AI agent evaluation tools. They check tool calls, trajectories, and whether a job still finishes. Promptfoo, DeepEval, Inspect, and Pydantic Evals are libraries you run locally or in CI. LangSmith, Langfuse, Braintrust, and Confident AI add hosted tracing and online evals. Phoenix is source-available under Elastic License 2.0 for self-hosting. This page does not invent a ranking.</p> <footer><a href="https://www.aiagentsinfo.com/best/ai-agent-evaluation-tools">Best AI agent evaluation tools</a>, AI Agents Info, last verified November 2026.</footer> </blockquote>