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AgentEval

Comprehensive .NET toolkit for AI agent evaluation featuring fluent assertions, stochastic testing, model comparison, and security evaluation built specifically for Microsoft Agent Framework

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In Plain English

A .NET framework for testing whether AI agents work correctly, stay secure, and deliver quality answers before you deploy them to production.

OverviewFeaturesPricingUse CasesLimitationsFAQAlternatives

Overview

AgentEval is the comprehensive .NET evaluation toolkit for AI agents, designed to be what RAGAS and DeepEval are for Python, but built natively for the Microsoft ecosystem. Specifically developed for Microsoft Agent Framework (MAF) and Microsoft.Extensions.AI, AgentEval provides sophisticated evaluation capabilities including tool usage validation, RAG quality metrics, stochastic evaluation, and model comparison with enterprise-grade fluent assertion syntax.

The framework's standout feature is its ability to assert on tool chains like requirements using intuitive Should() syntax, allowing developers to verify that agents call tools in the correct sequence with proper arguments and timing. This capability is crucial for complex agent workflows where the order and accuracy of tool execution determines success or failure.

AgentEval's stochastic evaluation capability addresses the non-deterministic nature of LLM responses by running the same evaluation multiple times and asserting on success rates rather than single runs, providing statistically meaningful results. This approach recognizes that LLMs can produce different outputs for identical inputs, making single-run evaluations unreliable for production assessment.

The platform includes innovative trace record/replay functionality that captures live API interactions once and replays them infinitely without API costs, enabling consistent CI/CD evaluation workflows. This feature eliminates the variability and expense of live API calls during testing while maintaining realistic evaluation scenarios.

AgentEval's Red Team Security module evaluates against 192 attack probes covering 6 OWASP LLM Top 10 vulnerabilities with MITRE ATLAS technique mapping, testing for prompt injection, jailbreaks, PII leakage, and other security vulnerabilities. This comprehensive security evaluation is essential for enterprise AI applications where security breaches can have severe consequences.

Model comparison features provide side-by-side evaluation of different models with cost-quality recommendations, helping teams make data-driven decisions about which models to deploy. The platform can compare performance across GPT-4o, Claude, and other major providers while analyzing the cost-benefit tradeoffs.

With MIT licensing and a commitment to remaining open source forever, AgentEval offers full type safety, compile-time error checking, and deep IDE integration that leverages the strengths of the .NET ecosystem for enterprise AI agent development. This makes it particularly valuable for organizations already invested in Microsoft's technology stack.

Compared to Python alternatives like DeepEval or LangSmith, AgentEval provides native .NET integration with superior type safety and enterprise development practices, making it ideal for organizations prioritizing reliability and maintainability in their AI evaluation infrastructure.

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Editorial Review

AgentEval fills a critical gap: production-grade AI agent testing for the .NET ecosystem. The stochastic evaluation, red team probes, and trace replay are genuinely useful. Limited to .NET, which narrows the audience but deepens the value for Microsoft-stack teams.

Key Features

Fluent Tool-Chain Assertions+

Uses a Should() syntax to assert that agents call tools in a required order with specific arguments, e.g., HaveCalledTool("AuthenticateUser").BeforeTool("FetchUserData").WithArgument("method", "OAuth2"). This replaces regex log-parsing with type-safe, IDE-autocompleted assertions that surface failures at compile time rather than in production.

Stochastic Evaluation Runner+

Executes the same test case N times (configurable via StochasticOptions(Runs: 10, SuccessRateThreshold: 0.85)) and asserts on aggregate statistics like success rate and standard deviation. This addresses the fundamental non-determinism of LLMs, replacing lucky-single-run pass/fail with statistically meaningful verdicts.

Trace Record/Replay+

The TraceRecordingAgent wraps a live agent once to capture all API interactions to JSON, after which TraceReplayingAgent returns identical responses forever with zero API cost. This enables deterministic CI runs, lets teams reproduce production failures offline, and eliminates flaky tests caused by live LLM variability.

Red Team Security Module+

Runs 192 attack probes across 9 categories including Prompt Injection, Jailbreaks, PII Leakage, and Excessive Agency, covering 6 of the OWASP LLM Top 10 2025 with MITRE ATLAS technique mapping. A one-line QuickRedTeamScanAsync() produces a 0–100 security score, and AttackPipeline.Create() allows granular intensity control plus PDF export for compliance reporting.

Model Comparison with Cost/Quality Recommendations+

CompareModelsAsync takes a list of model factories, test cases, and metrics (ToolSuccessMetric, RelevanceMetric, etc.) and returns a ranked markdown leaderboard. Output includes tool accuracy percentages, relevance scores, and cost per 1K requests, plus automated recommendations like "GPT-4o Mini — 87.5% accuracy at 50x lower cost" to drive data-driven model selection.

Pricing Plans

Open Source (MIT)

Free

  • ✓Full access to all core evaluation features
  • ✓Fluent assertions, stochastic evaluation, model comparison
  • ✓192-probe Red Team Security module
  • ✓Trace record/replay
  • ✓27 detailed code samples
  • ✓Community support via GitHub Issues and Discussions

Commercial & Enterprise (Planned)

TBA

  • ✓Optional add-ons on top of MIT core
  • ✓Not yet available — in planning phase
  • ✓Core will remain MIT and fully usable without these
  • ✓Details to be announced
See Full Pricing →Free vs Paid →Is it worth it? →

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Best Use Cases

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.NET teams building production AI agents on Microsoft Agent Framework who need compile-time-checked evaluation and automatic tool-call telemetry

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Enterprise security reviews requiring OWASP LLM Top 10 probing and MITRE ATLAS-mapped PDF compliance reports for auditors

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CI/CD pipelines where API costs and non-determinism make live LLM evaluation impractical — trace record/replay delivers free, deterministic runs

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Model selection projects comparing GPT-4o, GPT-4o Mini, Claude, and other providers with side-by-side accuracy-vs-cost leaderboards

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Multi-agent and multi-turn conversation testing requiring validation that tools are invoked in the correct order with correct arguments

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Performance SLA enforcement where TTFT under 500ms, total duration under 5s, and cost per call must be verified before production

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RAG system evaluation needing Faithfulness, Relevance, and Context Precision/Recall metrics with calibrated judge patterns

Limitations & What It Can't Do

We believe in transparent reviews. Here's what AgentEval doesn't handle well:

  • ⚠Requires .NET development skills and infrastructure — unusable by Python, JavaScript, Go, or Rust teams
  • ⚠Red Team security coverage is 60% of OWASP LLM Top 10 2025, so dedicated security scanners are still needed for the remaining 40% of attack categories
  • ⚠Stochastic evaluation multiplies LLM API spend if trace replay is not used for regression testing
  • ⚠No commercial support tier currently exists, which may block procurement at enterprises requiring vendor SLAs and paid incident response
  • ⚠Deep coupling to Microsoft Agent Framework means the project's roadmap follows Microsoft's direction rather than remaining provider-neutral

Pros & Cons

✓ Pros

  • ✓Native .NET integration with full type safety and compile-time error checking, unlike Python alternatives that rely on runtime exceptions
  • ✓Red Team module ships with 192 attack probes across 9 attack types covering 60% of OWASP LLM Top 10 2025 with MITRE ATLAS technique mapping
  • ✓Stochastic evaluation asserts on pass rates across N runs (e.g., 10 runs at 85% threshold) for statistically meaningful results
  • ✓Trace record/replay eliminates API costs in CI — record once with real API, replay infinitely for free with identical outputs
  • ✓Model comparison generates markdown leaderboards with cost/1K-request rankings across GPT-4o, GPT-4o Mini, Claude, and other providers
  • ✓MIT licensed with explicit public commitment to remain open source forever — no bait-and-switch license changes
  • ✓27 detailed samples included from Hello World through Multi-Agent Workflows and Cross-Framework evaluation
  • ✓First-class Microsoft Agent Framework (MAF) integration with automatic tool call tracking and token/cost telemetry

✗ Cons

  • ✗.NET-only — Python, JavaScript, and Go teams cannot use it and must rely on DeepEval, PromptFoo, or LangSmith instead
  • ✗Red Team coverage is 60% of OWASP LLM Top 10, leaving 40% of categories uncovered compared to specialized security scanners
  • ✗Commercial/Enterprise add-ons are still in planning phase, so enterprises requiring vendor SLAs and paid support have no tier to purchase
  • ✗Small community relative to Python-era evaluation tools means fewer third-party integrations, tutorials, and Stack Overflow answers
  • ✗Stochastic evaluation can become expensive — 100 tests × 50 repetitions equals 5,000 LLM calls per run if trace replay is not used
  • ✗Tight coupling to Microsoft Agent Framework concepts means evolving with Microsoft's roadmap rather than remaining provider-neutral

Frequently Asked Questions

Can I use AgentEval with Python agents?+

No. AgentEval is built exclusively for .NET and ships on NuGet (nuget.org/packages/AgentEval). Python teams should use DeepEval, PromptFoo, or LangSmith for equivalent AI agent evaluation capabilities. Based on our analysis of 870+ AI tools, AgentEval is one of the only mature agent evaluation frameworks targeting the Microsoft/.NET ecosystem specifically, which is precisely its positioning.

Does AgentEval work with agents not built on Microsoft Agent Framework?+

Yes. Any .NET agent that implements IChatClient can be tested via the IChatClient.AsEvaluableAgent() one-liner extension method. A Semantic Kernel bridge is also included for SK-based agents. This cross-framework design means you are not locked into MAF, though MAF is where the deepest integration exists with automatic tool call tracking and token/cost telemetry.

How does AgentEval compare to DeepEval and RAGAS?+

DeepEval and RAGAS are Python frameworks with larger communities and broader metric catalogs. AgentEval is their .NET counterpart, offering equivalent coverage for RAG metrics (Faithfulness, Relevance, Context Precision/Recall), plus unique additions like the 192-probe Red Team module and fluent tool-chain assertions. Choose based on language ecosystem — AgentEval for C#/.NET shops, DeepEval/RAGAS for Python. All three are open source.

How much does stochastic testing cost in LLM API fees?+

It scales with repetition count: 100 tests × 50 repetitions equals 5,000 LLM calls, roughly $15–$30 per test suite at GPT-4 pricing. AgentEval's recommended pattern is to use live stochastic evaluation only for new scenarios and switch to trace record/replay for regression testing in CI, which eliminates API costs entirely. The comparer's RunsPerModel option (typically 5) gives statistical stability without runaway cost.

What security vulnerabilities does the Red Team module detect?+

The Red Team module runs 192 attack probes across 9 attack types: Prompt Injection, Jailbreaks, PII Leakage, System Prompt Extraction, Indirect Injection, Excessive Agency, Insecure Output Handling, API Abuse, and Encoding Evasion. This covers 6 of the OWASP LLM Top 10 2025 vulnerabilities (60% coverage) with MITRE ATLAS technique mapping, and results can be exported directly to PDF for compliance reporting via result.ExportAsync("security-report.pdf", ExportFormat.Pdf).
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What's New in 2026

AgentEval launched in 2025–2026 targeting the newly released Microsoft Agent Framework (MAF) and Microsoft.Extensions.AI. Recent additions include the 192-probe Red Team Security module with OWASP LLM Top 10 2025 coverage and MITRE ATLAS technique mapping, a universal IChatClient.AsEvaluableAgent() cross-framework bridge, a Semantic Kernel integration bridge, and the agenteval CLI tool. Commercial/Enterprise add-ons are on the roadmap but not yet released.

Alternatives to AgentEval

DeepEval

Testing & Quality

DeepEval: Open-source LLM evaluation framework with 50+ research-backed metrics including hallucination detection, tool use correctness, and conversational quality. Pytest-style testing for AI agents with CI/CD integration.

LangSmith

Analytics & Monitoring

LangSmith lets you trace, analyze, and evaluate LLM applications and agents with deep observability into every model call, chain step, and tool invocation.

Promptfoo

Testing & Quality

Open-source LLM testing and evaluation framework for systematically testing prompts, models, and AI agent behaviors with automated red-teaming.

View All Alternatives & Detailed Comparison →

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