TruLens is an open-source system for tracing and evaluating LLM applications and AI agents. It records each step's inputs, outputs, latency, tokens, and cost, then uses evaluations to find failures and compare application versions.
Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add truera/trulens --skill trulens-evaluation-workflowgit clone --depth 1 https://github.com/truera/trulensWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/truera/trulens/trulens-evaluation-workflow)<a href="https://agentmods.dev/skills/truera/trulens/trulens-evaluation-workflow"><img src="https://agentmods.dev/badge/skills/truera/trulens/trulens-evaluation-workflow/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/truera/trulens/trulens-evaluation-workflow"><img src="https://agentmods.dev/badge/skills/truera/trulens/trulens-evaluation-workflow.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector pass
What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00018 | $0.01665 |
| Opus 5 | $0.00009 | $0.00833 |
| Sonnet 5 | $0.00004 | $0.00333 |
| Haiku 4.5 | $0.00002 | $0.00167 |
Grade A, and why
trulens-evaluation-workflow scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 9d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 182 lines — stays where its author put it; the contents beside it link to each section on GitHub.
TruLens Evaluation Workflow
A systematic approach to evaluating your LLM application.
When to Use This Skill
Use this skill when you want to:
- Set up comprehensive evaluation for a new LLM app
- Improve an existing app's evaluation coverage
- Understand the full TruLens workflow
- Know which sub-skill to use for your current task
Required Questions to Ask User
Before implementing, always ask the user these questions:
1. App Type (determines instrumentation wrapper)
- What framework is your app built with? (LangChain, LangGraph/Deep Agents, LlamaIndex, Custom)
2. Evaluation Metrics (determines feedback functions)
Ask: "Which evaluation metrics would you like to use?"
| App Type | Recommended Metrics | Description |
|---|---|---|
| RAG | RAG Triad | Context Relevance, Groundedness, Answer Relevance |
| Agent | Agent GPA | Tool Selection, Tool Calling, Execution Efficiency, etc. |
| Simple | Answer Relevance | Basic input-to-output relevance check |
| Custom | Ask user | Let user describe what they want to evaluate |
For Agents, also ask:
- Does your agent do explicit planning? (determines if Plan Quality/Adherence metrics apply)
3. Additional Metrics (optional)
- Do you want any additional evaluations? (Coherence, Conciseness, Harmlessness, custom metrics)
The Evaluation Workflow
┌─────────────────────────────────────────────────────────────────┐
│ TruLens Evaluation Workflow │
├─────────────────────────────────────────────────────────────────┤
│ │
│ 1. INSTRUMENT 2. CURATE 3. CONFIGURE │
│ ┌──────────────┐ ┌──────────────┐ ┌──────────────┐ │
│ │ Capture data │ → │ Build test │ → │ Choose │ │
│ │ from your │ │ datasets │ │ metrics │ │
│ │ app │ │ │ │ │ │
│ └──────────────┘ └──────────────┘ └──────────────┘ │
│ ↓ ↓ │
│ └─────────────────────┬─────────────────────┘ │
│ ↓ │
│ 4. RUN & ANALYZE │
│ ┌──────────────┐ │
│ │ Execute evals│ │
│ │ & iterate │ │
│ └──────────────┘ │
│ │
└─────────────────────────────────────────────────────────────────┘
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 9d ago First seen · 182 lines · 18 tokens per session scan A 27ca90d0e52b
trulens-evaluation-workflow is a skill published in the GitHub repository truera/trulens (3,536 stars, last pushed 4d ago), licensed MIT. It adds 18 tokens to every session and 1,665 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
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