AI Engineer Summit
November 11, 2026Online track4 min read

Your SKILL.md is 70% of Things the Model Already Knows

A skill can teach an agent something it does not know, or it can steer the agent through a process it already understands.

Nikolay Petrov

Day 1 livestream · 7:00:53–7:14:53 on YouTube. The player starts and stops at this session’s boundaries.

Introduction

A skill can teach an agent something it does not know, or it can steer the agent through a process it already understands. Nikolay Petrov starts by keeping those purposes separate. Both can be useful. His talk asks how to measure the first kind of value without assuming that every sentence in a successful skill supplies new knowledge.

That distinction is essential to the title. “The model already knows this” is not the same as “this instruction is useless.” A reminder can constrain behavior even when it introduces no new concept. Petrov's proposal is a diagnostic for optimization, followed by task evaluation, not a license to delete most of every skill file.

7:02:13 ↗

Begin with tasks, not a feeling that the skill helps

At 07:02:13, Petrov describes the ordinary with-skill/without-skill comparison. Define tasks, preferably with outcomes that can be checked deterministically, and run both arms. His illustrative example goes from three solved tasks out of five to all five. Token usage and completion time can matter alongside the solve rate.

This establishes that a skill helps, but not which pieces are responsible. Once the model changes or the skill grows, editing line by line becomes an expensive guessing exercise. Petrov wants a smaller unit of analysis than the whole document and a more meaningful unit than an arbitrary line break.

7:04:53 ↗

Break the instructions into testable atoms

Around 07:04:53, he introduces atomic items inspired by fact-oriented evaluation. Each item becomes a question paired with the expected answer. Some items express general propositions; others specify contracts, such as exact required behavior or conditions.

For each item, the system queries the target model both with and without the skill. A judge, preferably from a different model family or a panel, grades the answers. Question construction must avoid leaking the answer. The experiment can also distinguish closed-book knowledge from practical performance with tools such as web access, depending on what is being measured.

The two arms produce four useful cases:

  • Correct in both: the model can answer without the skill.
  • Correct only with the skill: the skill supplies useful information.
  • Correct only without the skill: the added context hurts this answer.
  • Incorrect in both: the skill has not successfully taught the tested item.

These are observations about the question and evaluation setup. They do not by themselves establish how the agent will behave in a long, tool-using task. They do identify where to investigate first.

Fix harm before chasing compression

Petrov turns first to the third category. Material that degrades an answer is a strong candidate for revision. In the popular skills he tested, he says this was uncommon, but less-developed skills showed more such problems. The method can color portions of a document according to their contribution, exposing where a skill adds information and where it restates known concepts.

He also addresses the cost of running the diagnostic, reporting a roughly $14 experiment across twenty-nine skills. That is an account of his setup, not a stable pricing promise. The practical attraction is that a targeted assessment can be cheaper than repeatedly trying arbitrary combinations of edits against the full task suite.

7:10:09 ↗

Knowing the concept is not knowing the exact rule

At 07:10:09, Petrov changes the grading standard. Lenient grading accepts the general idea even if a detail is missing. Strict grading requires the full condition or instruction. The distinction dramatically changes the apparent amount of knowledge already present in the model.

General understanding and exact instruction recall differ Original stream, 7:10:50. In the displayed comparison, Opus 5.5 drops from 70% to 22% of atoms known without the skill when grading becomes strict.

The slide gives a particularly useful example: knowing that the user makes the decision is not the same as knowing to put each decision to the user and wait. Omitting the wait can fail a behavioral contract even though a lenient judge recognizes the general principle.

The displayed Haiku 5.5 result falls from 45% to 18%; Opus 5.5 falls from 70% to 22%. Petrov's interpretation is that larger models often know the concepts while still benefiting from precise keys, values, conditions, and steps. The headline 70% therefore depends on what counts as knowing, which model is tested, and which skills are included.

Use novelty to propose edits, then rerun the real evaluations

Petrov next compares repositories and models, emphasizing that the amount of prior knowledge varies by skill. A directional process skill may reasonably contain familiar material. A knowledge skill targeting a smaller model may need explanations that a larger model can supply unaided. There is no single minimal skill independent of the model and job.

His closing procedure returns to the task evaluations from the opening. Remove or rewrite candidate material, then check whether the skill still solves the intended problems. If scores hold while the document shrinks, the saved context is real. If behavior deteriorates, apparent redundancy was doing useful work.

The framework he demonstrates can also examine routing, descriptions, and other context artifacts, but novelty is only one signal. The contribution of this talk is an intermediate layer between intuition and brute-force prompt editing: identify which atomic instructions are new, harmful, or still not understood, then use that evidence to choose experiments. A shorter SKILL.md is a successful outcome only if the agent continues to do the work.

Full transcript 285 timestamped passages

Machine-generated source transcript; recognition errors remain. Timestamps and subtitles use the selected source recording’s clock, not clip-relative time. Section links use cited source moments; sections without a verified moment return to the talk start.

7:00:53>> Hello, my name is Nikolai Petro and we

7:00:55will be talking about skills and agents

7:00:57knowledge of those skills.

7:01:01We'll start it with the simple prompts

7:01:03where we've been playing with the new

7:01:06stuff, new work being done by the

7:01:08agents, repeating those prompts over and

7:01:10over again. And then we start packing

7:01:12those into the skills,

7:01:14creating repeatable, reproducible,

7:01:17portable type of their functionality

7:01:21or capabilities that we can teach agents

7:01:25to work with. And some of those skills

7:01:27are very important. hundreds of the

7:01:28stars on GitHub.

7:01:33There are different types of their

7:01:34skills. Some teach models something new

7:01:38bringing new knowledge or capabilities

7:01:40to the model. But there are also types

7:01:43of their just steering or process skills

7:01:46where we

7:01:48do not bring any additional information

7:01:50but just getting repeatable

7:01:53flow of the actions that we want agents

7:01:55to perform. both are useful. In this

7:01:59session, we will be talking about new

7:02:01knowledge type of the skills and

7:02:05we'll see what we can

7:02:08get from the models understanding of

7:02:10those skills.

7:02:13So, we get our first skills packed,

7:02:16start using them. Um, basically

7:02:21starting with the the feel of does it

7:02:24work or not. But there is also the more

7:02:26technical way and more deterministic way

7:02:28for the checking if skills are working

7:02:30or not and what's the impacts of those

7:02:33skills are evolves. There are different

7:02:36formats where evolves can be defined.

7:02:39But at the sense this is task definition

7:02:41that you want your agent to be able to

7:02:44solve.

7:02:46You put it in the place ideally more

7:02:48deterministic so we can uh validate it

7:02:51and we can check two arms one there no

7:02:56skill loaded and there second one where

7:02:58we're loading the skill and providing

7:02:59this additional information to the

7:03:01context and we compare how the runs

7:03:04there are multiple things one is how

7:03:07many

7:03:08evolves been solved in this case with no

7:03:11skill we're solving three out of five

7:03:14with skill we're solving all five

7:03:16meaning that we get two more tasks.

7:03:19There also would be implications on the

7:03:21tokens usage or time that it took those

7:03:25tasks to be completed and other factors.

7:03:28But at the end we are comparing those

7:03:30and seeing what makes sense, what not.

7:03:32And this is one of the mains for

7:03:35evaluating the skills and uh saying that

7:03:38they not just nice ideas but actually

7:03:41working pieces of instructions and

7:03:43context for the agents.

7:03:46But what next? We get to the stage where

7:03:50we have their working skill. It solves

7:03:52some evolves. But we know that there

7:03:57should be a better way. We have models

7:03:59evolving. We have u some

7:04:03might be cases where we want

7:04:07to get skill more efficient meaning

7:04:10consuming less tokens. So what's their

7:04:12the options there? One is just change

7:04:15line by line and try brute force all the

7:04:20different combinations. Another would be

7:04:23to think through what makes sense. So

7:04:25maybe use something as the user feedback

7:04:29on the skills to see where the skills

7:04:32perform well. Uh there it's not. And

7:04:35with new models just running skill and

7:04:38seeing how it works, what's the options

7:04:41there? and how large those modifications

7:04:45should be just

7:04:47lines, sentences, ideas.

7:04:53So what we found to be useful is instead

7:04:57of relying on their luck, we can put

7:05:00more deterministic process here using

7:05:03idea of their items from their fact

7:05:06score. uh

7:05:08we can split their skill and

7:05:11instructions into those items and

7:05:16for each of those had the pair of

7:05:19question and answer that we expect.

7:05:22This could be either general ideas like

7:05:25proposition in this case or contracts

7:05:28there we put more definitive expectation

7:05:32on their action

7:05:37and in general we will be getting their

7:05:43some predefined amount of the items per

7:05:46skill and we will have let's say

7:05:5025 or 30 items arms per skill.

7:05:54Then for each of the items, we will

7:05:57again run two arms, one without skill

7:06:00and one with skill.

7:06:03And we will have judge or panel of

7:06:07judges that will be evaluating model

7:06:09answers. So we asking those questions to

7:06:11the model that we're interested in.

7:06:14We evalating those questions with the

7:06:17judge ideally different family of the

7:06:20models or panel of judges also ensures

7:06:24that the question do not leak answers.

7:06:29We depending on the case can compare

7:06:32with no tools or additional um

7:06:35information to check their internal

7:06:37model understanding or provided with

7:06:40their some tools like web access. So uh

7:06:43it would be more practical

7:06:45and we

7:06:48can get the simple four outcomes matrix

7:06:55basically where we are checking that the

7:06:57model

7:06:59uh knows or do not know something and

7:07:03how this maps to their skill impact on

7:07:05this. So the simplest option is where

7:07:09model was able to answer this particular

7:07:13questions even without skill or with

7:07:16skill. This means that skill have no

7:07:18impact on this and this was already part

7:07:20of the model's knowledge. The second one

7:07:23is where without skill actual model was

7:07:25able to answer this correctly

7:07:28and by adding skill we saw degradation

7:07:32in performance and model capability to

7:07:35talk or explain particular aspects.

7:07:40The ideal case is where without skill

7:07:43model wasn't able to answer something

7:07:44and with skill we start seeing that it

7:07:47can answer those new type of the

7:07:49questions and scenarios and this is what

7:07:51we were aiming for teach model something

7:07:53new

7:07:55but there also can be the fourth option

7:07:57where skills were written not ideally or

7:08:03in some maybe not clean way where model

7:08:08wasn't able to answer it either without

7:08:10skill or with skill. And while this

7:08:12topic might be relevant and important

7:08:14for the model, it still sort of misses

7:08:16some of those concepts.

7:08:21The simplest thing to fix are

7:08:26instructions or items that actually hurt

7:08:28performance. And

7:08:31for popular skills, those are criteria.

7:08:34So in the

7:08:37uh box below you see that it's just one

7:08:41case out of the mostly 400 items in

7:08:45entropic skills and others don't have

7:08:48those. But for their smaller skills that

7:08:52are less popular, you probably having

7:08:54more of those. This is what we're seeing

7:08:55with some of our experiments.

7:08:59And

7:09:01this is just straightforward the

7:09:03simplest thing to fix to ensure that

7:09:06your skill do not reduce model

7:09:08capabilities and performance and bring

7:09:10only relevant

7:09:12context there.

7:09:15And we also can actually color this. In

7:09:17this scenario, this is done by lines but

7:09:20actually going with it atoms. You might

7:09:22have their uh different coloring for a

7:09:24single line or a single sentence.

7:09:28And this just gives your example of

7:09:30their uh visualization where this would

7:09:34be helpful details and instructions in

7:09:37terms what new stuff you bring to the

7:09:40model and what is

7:09:45something that model already knows.

7:09:48Costwise

7:09:49we are running all those questions and

7:09:51asking model

7:09:53but still relatively this is uh cheap

7:09:56for 29 skills 14 bucks of their set and

7:09:59ha calls with their sonet used as a

7:10:03judge

7:10:05and

7:10:09there are couple ways how we also can

7:10:12check their strictness of their some

7:10:16knowledge. Um we have uh lang and strict

7:10:20ways of the checking this where first

7:10:23checks the general idea while the second

7:10:26one is checking for exact details and

7:10:30you can think about the difference

7:10:32between general knowledge and

7:10:33understanding of the topic to the

7:10:36understanding of the exact keys

7:10:38parameters and exact values or steps.

7:10:43And what we see across the models is the

7:10:46difference is large especially with the

7:10:51um larger frontier models where we see

7:10:53almost dropping from 70% understanding

7:10:55of their skill in case of the general

7:10:58understanding to just 22% of the

7:11:02specific details.

7:11:05And this is much our expectations. We

7:11:08see that new models are pretty well

7:11:10generalized to understand concepts but

7:11:13it's still helpful to provide their with

7:11:15exact details and data that will be

7:11:17useful for their solving those problems.

7:11:23Here is outlook of their um comparing

7:11:28those three popular repos with the

7:11:30skills across different models. So one

7:11:34of the interesting observations here is

7:11:36that smaller model have in general lower

7:11:40understanding of the

7:11:43skill

7:11:45with their larger sonet having better

7:11:47understanding which is

7:11:50why we have bigger models. But also we

7:11:53see that overall their models already

7:11:55understand a lot of their

7:12:01details and context of those skills. And

7:12:03you would expect that with the newer

7:12:05models and more advances in their uh

7:12:09better training capabilities we will

7:12:11have more and more

7:12:14uh in terms of the models understanding.

7:12:17But also we see that this pretty

7:12:19significantly differs skill to skill

7:12:22and it's not bad. Some skills are

7:12:25intended to be directional

7:12:28but it's also useful piece of

7:12:30information to see how those

7:12:33skills bring new knowledge uh to the

7:12:36different model and different families.

7:12:38And uh this should be run ideally in the

7:12:40broader set of the models.

7:12:48But just having their

7:12:52this novelty piece of information is

7:12:56just one of the signals. It's basically

7:12:57initial vector for optimization. At the

7:12:59end we still have to run evolves and

7:13:02validate that all the changes that we

7:13:06try make with their skill actually

7:13:08works.

7:13:10So the one of their simpler scenarios

7:13:12would be we can look on their skill and

7:13:16try to remove some or all of the already

7:13:20known pieces of information from the

7:13:22skill and run evalation.

7:13:26It might come up with their same

7:13:27scoring. Basically we will be getting

7:13:30their same results model still capable

7:13:31of solving those problems. Then great we

7:13:34can reduce skill size safe tokens safe

7:13:37context.

7:13:39And instead of there brute forcing and

7:13:42guessing what we can or should remove or

7:13:45add or how to fix their uh

7:13:49degradations, we can have a guidance.

7:13:54So all of those measurements experiments

7:13:57been done with the document which is a

7:14:00framework for the comparing

7:14:02everything related to the agents and

7:14:04context

7:14:06where it's is scale agents MD MCP tools

7:14:10whatever and novelty is one of their

7:14:14pieces of the functionality where you

7:14:16can get this initial vector for their

7:14:19skill optimization and evalation but

7:14:21there also uh evolves there Assessment

7:14:25of the context impact, routing,

7:14:27comparing the uh descriptions, naming,

7:14:31bunch of the things that related to the

7:14:35skills where it would be helpful to

7:14:38actually get there more deterministic

7:14:39relations to make conscious decisions in

7:14:42terms of what should be done with the

7:14:44skills.

7:14:47So, thank you for your time and please

7:14:50go ahead and write better skills.