Validates dataset formatting and quality for SageMaker model fine-tuning (SFT, DPO, or RLVR).
SkillScore73Maintained
Automatic
◆AI Engineer pack
Last verified 8/16/2026
What it changes
Passed 12 of 17 test cases with the skill, and 4 of 17 without it.
Without skill23%
With skill73%
Checks it passed that the model alone missed
The response specifies running python scripts/format_detector.py dataset/data.jsonl.
The response requests user confirmation before proceeding with any transformation plan.
The response specifies executing format_detector.py with only the dataset path as an argument.
and 9 more in the full report
11 fixed5 passed either way6 still failing0 broke
Pass-rate lift
+50 pp
Tokens
+8%
Agent turns
0%
Response time
-49%
Model gemini-3.6-flashMeasured 8/16/2026v116 of 22 cases passed with skill · 17 comparable
Tokens, turns and time describe resource use, not a dollar price.
See it in action
One of 10 test cases the skill fixed. Same model, same prompt, with and without the skill.
1 of 10
Prompt
I have a local file dataset/data.jsonl. What is the exact command used to execute format detection on this file?
What was checked, without and with the skill
Checked
Without skill
With skill
The response specifies running python scripts/format_detector.py dataset/data.jsonl.
Missed
Passed
case-12 · gemini-3.6-flash · 8/16/2026 · answers are capped and redacted
What's inside
The instructions your model reads when the skill loads.
SKILL.md64 lines4 filesincludes scripts
Workflow Instruction
Follow the workflow shown below. Locate the dataset, check the file type, and resolve any issues with missing files or wrong file types. Determine the fine-tuning model and fine-tuning strategy. Run the appropriate validation based on the model family. Summarize the results: is the dataset ready for fine-tuning?
Prerequisites
The SDK environment has been verified (SDK version, region, execution role). If not done, activate the sdk-getting-started skill first.
Workflow
Locate Dataset:
The full path may be a local file path, or an S3 URI
Resolve the full path to the dataset file, make sure read permissions are available, and help the user if the file is not found
Determine strategy and model:
File formatting depends on the currently selected fine-tuning strategy and fine-tuning base model.
If the strategy and model are already known from the conversation context (e.g., selected via the model-selection and finetuning-technique skills), use them.
If not available in context, activate the model-selection and/or finetuning-technique skills to determine them before proceeding.
Exception: If the user is validating an evaluation dataset (not a training dataset), neither model nor technique is required — the format detector can validate eval format (query/response structure) independently. Do not block on model-selection or finetuning-technique for eval dataset validation.
Check File Formatting: Run the tool format_detector.py to make sure the file conforms to formatting requirements.
Send the full path directly to the format_detector script as an argument
Do not send the model and strategy as arguments
Do not download data from S3
Do not make local copies of data
Summarize Results: Tell the user if their data is ready
Examine the output of format_detector and compare to the known strategy and model
Important: training datasets and evaluation datasets have different format requirements.
Training datasets must match the fine-tuning strategy format per references/strategy_data_requirements.md
Custom Scorer evaluation datasets have scorer-specific requirements. If the dataset is intended for Custom Scorer evaluation (Prime Math, Prime Code, or Custom Lambda), read references/custom-scorer-evaluation-dataset-formats.md and validate against the scorer-specific schema. The scorer type should be known from conversation context (determined in the model-evaluation skill).
Report back to the user if their current dataset is valid for its intended purpose
Warn the user if their dataset is valid, but for a different strategy or model
Warn the user if their dataset is not valid for any strategy/model pair
If the user plans to finetune a model with the evaluated dataset, it needs to be uploaded to an S3 bucket in the same region as the planned training job (usually the default region). Warn the user if this is NOT the case.
If the dataset is NOT in the necessary format, recommend transforming it using the dataset-transformation skill, wait for user confirmation, and update the plan based on their response