When to Use a Notebook
Before choosing to use a notebook, evaluate the task complexity using these heuristics.
Use a notebook if you meet at least one of these criteria:
- 📈 Data Insights & Storytelling: Use a notebook for any request to "give insights", "find trends", "explore data", or "analyze data". These tasks benefit from using visualizations to present the data.
- 📊 Visualizations are requested: The user explicitly asks for charts or plots.
- 🔄 Stateful / Iterative Exploration: You need to run a query, inspect results, and decide the next query based on those results while keeping state in memory.
Do NOT use a notebook ONLY if:
- 📝 Simple Fact/Status: The request only requires a single number (e.g., "how many rows") or a status check (e.g., "when was this table updated").
- 🏃♂️ Schema Preview: The request is only about the schema or field types.
Golden Rule of Data Storytelling: If any analytical insight, trend, or comparison is involved, favor a notebook and a visualization. A notebook is the "standard" environment for our developer workflow; do not avoid it because of "overhead".
Notebook Best Practices
[!IMPORTANT]
Agent execution rules: Your behavior MUST depend on whether the
notebook_execute_celltool is available in your current context: * If notebookexecute_celltool is available: You MUST follow the incremental GENERATE CELL -> EXECUTE CELL -> VALIDATE flow. * If notebookexecute_celltool is NOT available: You MUST generate the complete notebook and request user execution.
- CONDITIONAL EXECUTION FLOW:
- If notebook
execute_celltool is available: Follow the STEP BY STEP GENERATE CELL -> EXECUTE CELL -> VALIDATE OUTPUT flow. Generate ONE cell, execute it, then verify the output. If the output is data (e.g. a dataframe), you MUST inspect it to confirm the logic is correct before generating the next step. Batch generation of an entire notebook is strictly prohibited because error propagation in notebooks is expensive to fix. - If notebook
execute_celltool is NOT available:- Create the whole notebook at once.
- Tell the user to run the notebook.
- Tell the user to let you know once the notebook run is completed so you can check the outputs to verify it's correct and fix any errors.
- If notebook
- IDENTIFY DATA EARLY: Use
@skill:discovering-gcp-data-assetsor BigQuery list tools to find the correctproject.dataset.tablebefore writing ANY code. If the table ID is missing, ask the user. - CLEAN FINAL STATE: The final notebook MUST NOT have failed cells. If a cell fails, you MUST fix it. If you tried several versions, delete the failed attempts before you present the notebook to the user.
- LOGICAL CHUNK FIDELITY: Keep cells small. One logical transformation or
visualization per cell. Group related cells into logical units (e.g., a
BigQuery
%%bqsqlmagic cell followed immediately by a Python visualization cell for those results). Use descriptive markdown cells to separate and document different logical sections. - GENERATE VISUALIZATIONS: Always accompany data insights with visualizations; charts are often more effective than raw numbers for communicating trends and comparisons.
Kernel & Environment Management
Notebooks run in specific Kernels (execution backends). You MUST ensure the
kernel’s Python environment contains the necessary libraries (bigframes,
ipykernel, etc.).
Kernel Types
- Local Python: Standard Python 3 kernel running on the notebook host (Managed instance, local machine).
- Cloud Spark Remote (Dataproc Serverless): Transient Spark environment managed by GCP. Use for large-scale data processing.
- Cloud Spark Remote (Dataproc Cluster): Persistent Spark clusters for shared or custom configurations.
- Colab (Managed): Ephemeral Google-managed runtimes.
No Active Kernel / Setup Check
- Infer or Ask about Kernel Preferences:
- Infer from notebook purpose:
- Only "Spark" notebooks may use a Remote Spark kernel. "BigFrames" and "BigQuery" notebooks MUST use Local Python.
- Infer from notebook cells:
- Presence of a Spark Connect session, for example
ManagedSparkSessionorDataprocSparkSession, indicates Local Python.
- Presence of a Spark Connect session, for example
- Infer from notebook metadata:
- Read the
metadata.kernelspecnotebook field. A Remote Spark kernel name starts with a connection hash.
- Read the
- Infer from Context:
- For a "Spark" notebook, evidence of a local Python setup (such as a Spark Connect session) means you should lean towards Local Python. Without such evidence, lean towards Remote Spark.
- Ask when Ambiguous: If multiple options fit, ask if they prefer a Local Python or a Remote Kernel.
- Infer from notebook purpose:
- For Local Setup: Use
@skill:managing-python-dependenciesto verify if a virtual environment exists. If not, create one. Ensureipykernelis installed in that environment. Install any other relevant libraries. - For Remote Setup: Advise the user to use the UI to select the appropriate remote kernel.
[!IMPORTANT]
HARD STOP on kernel failure: If a cell execution returns "no active kernel" or any kernel-not-found error, you MUST stop immediately. Do NOT scaffold, generate, or insert any further cells. Inform the user which kernel is needed (e.g., PySpark / Dataproc Serverless) and wait for explicit confirmation that a kernel is active before proceeding with notebook execution.
Proper Library Installation
1. Local Kernels
Before installing any python libraries, you MUST use
@skill:managing-python-dependencies to detect how python dependencies are
managed in the project.
2. Remote Kernels (Spark/Colab)
Since these are often ephemeral or managed by GCP:
- Check first (REQUIRED): Before writing any
%pip installcell, run%pip listorimport <package>to confirm the package is not already present. Managed runtimes (Dataproc Serverless, Colab) pre-install many common packages. Only install what is confirmed missing. - Use
%pip install <package>in the first cell if a package is confirmed missing and it's the only way to modify the runtime.
When in doubt about the kernel type or preferred installation method, ask the user for clarification.
Data Analysis & Visualization Rules
Guidelines for performing exploratory data analysis, data cleaning, and visualization in notebooks.
Notebook Layout
The notebook should read like a story. While you have flexibility (e.g., multiple visualizations for one data cell, or data cells building on each other), aim for this general flow:
- Title & Objective (Markdown Cell)
- What is this notebook for? (e.g.,
# Retention Analysis)
- What is this notebook for? (e.g.,
- Section Header (Markdown Cell)
- What are we looking at now? (e.g.,
## Exploring User Retention)
- What are we looking at now? (e.g.,
- Data Acquisition/Transformation (Python cell, may contain
%%bqsqlmagics)- Query BigQuery or transform data.
- Verification (Optional but Recommended) (Python Cell)
df.head()or assert sanity checks.
- Visualization (The Goal) (Python Cell)
- Plot the insight (e.g.,
df.plot()).
- Plot the insight (e.g.,
Repeat steps 2-5 for each new sub-topic or insight. You can have multiple Data cells before a Visualization, or multiple Visualizations from one Data cell. The key is to keep them grouped logically and separated by Markdown headers.
-
Final Summary (Markdown Cell)
- At the end of the notebook, add a markdown cell containing a summary paragraph that summarizes the findings to the user. The summary MUST follow these guidelines:
- MUST NOT add Python code to the summary.
- The summary MUST NOT start with a code block.
- The summary MUST be strictly grounded in the numerical data verified in the notebook.
- The summary MUST ONLY contain the following three sections:
-
Q&A If the data analysis task contains questions (implied or
explicit), you MUST answer them based on the solving process. Skip this section if there are no questions to answer. -
Data Analysis Key Findings Summarize the key analysis findings
in bullet points, it's a plus to quote the numbers in the previous steps. Only report high-value findings, skip the obvious ones. -
Insights or Next Steps Provide 1-2 concise insights or next
steps in bullet points.
-
-
Next Steps: After the notebook has been successfully executed and verified, and the summary is complete, notify the user and propose next step suggestions.
Plotting Rules
- You MUST use different colors for different features to ensure plots are readable for humans.
- When creating a plot, you MUST adjust the figure size based on the number of features. The labels and legends MUST NOT overlap.
- You SHOULD arrange the layout wisely. Using subplots CAN help in placing different plots effectively.
- You MUST use inline figures to present figures and plots along with code and text in the notebook.
- For clustering, use PCA to reduce to 2D before scatter plotting.
- Use Line Charts ONLY for continuous data (e.g. time series) where interpolation between points is meaningful.
Data Cleaning Rules
- You MUST be careful about missing values and duplicated values.
- You MUST NOT drop columns unless absolutely necessary. Dropping columns is irreversible.
- You SHOULD focus on columns directly related to accomplishing the task; not every column NEEDS to be cleaned.
Cell Execution
When a notebook cell execution tool is available (exposed as
notebook_execute_cell or notebook__execute_cell), you MUST use it to
create and execute cells one at a time. You MUST NOT generate .ipynb
files programmatically (for example with nbformat) or execute notebooks in
batch from the shell (for example jupyter nbconvert --execute or
papermill).
For Local Python execution, you MUST use a virtual environment and the Python version inferred from the kernel definition.
Cell Execution Failure Handling
[!CAUTION]
When a cell fails, the agent MUST follow the protocol below. The agent MUST NEVER silently work around failures by fabricating data, substituting models, or changing infrastructure. Fake outputs that look correct are worse than a visible error.
1. Retry Transient Failures
Retry the cell once only if the error is plausibly transient (timeout,
DEADLINE_EXCEEDED, UNAVAILABLE, kernel restart, rate limit). Re-invoke the
cell execution tool with the exact same parameters: do NOT edit the code,
change the kernel, or alter any tool argument first. If it fails again with the
same or substantially similar error, the failure is confirmed. For
deterministic errors (SyntaxError, NameError, ModuleNotFoundError,
PERMISSION_DENIED, NotFound) skip the retry entirely. Proceed to step 2.
[!WARNING]
Before retrying, you MUST consider whether the cell is safe to re-run. If the cell has side effects (writes or appends to a table or bucket,
INSERT, DDL, an incrementing counter, a mutating API call) it may have partially succeeded before failing. In that case you MUST NOT blindly retry: report the situation to the user, or first verify or undo the partial effect.
2. Classify the Failure
Categorize the confirmed failure to determine whether the agent is allowed to fix it autonomously:
Syntax / Logic Error
- Examples:
SyntaxError,NameError, typos in column names, wrong API usage. - Agent May Fix: YES — fix the code.
Missing Library
- Examples:
ModuleNotFoundError,ImportError. - Agent May Fix: YES — install it using
@skill:managing-python-dependencies.
Infrastructure / Access Failure
- Examples: permission denied on GCS/S3, unreachable Spark cluster manager, missing credentials, VPC/firewall errors.
- Agent May Fix: NO — STOP and ask the user.
Missing Data or Model Artifact
- Examples: file/table/bucket not found, model path does not exist, empty dataset.
- Agent May Fix: NO — STOP and ask the user.
Kernel / Runtime Incompatibility
- Examples: Java version mismatch, unsupported Python version, class version errors.
- Agent May Fix: NO — STOP and ask the user.
3. Prohibited Workarounds (NEVER DO THESE)
The following actions are strictly forbidden as remediation for a failing cell. Violating any of these produces misleading outputs that the user cannot trust.
- No Fabricating Data — Never generate synthetic/sample data to replace a
dataset that failed to load. Never use
spark.createDataFrame(...)orpd.DataFrame(...)with made-up rows as a substitute for real data sources. - No Substituting Models — Never train a placeholder/dummy model to
replace a pre-trained model that failed to load. Never swap model types
(e.g.,
RandomForestClassifierforXGBClassifier) just to make the cell pass. - No Silently Changing Infrastructure — Never switch
master("spark://...")→master("local[*]"). Never replacegs:///s3://paths with local filesystem paths. Never swap a remote database connection for a local file. - No Downgrading the Execution Environment — Never replace a remote/managed Spark session with a local PySpark session.
- No Rewriting Cell Intent — Never change what a cell fundamentally does (e.g., turning "load from GCS" into "generate locally"). Minor syntax/API fixes are allowed; replacing the data source is not.
- No Silently Reducing Data Scope — Never add or lower
LIMITclauses, filter predicates, or sampling to work around timeouts or resource errors without explicit user approval. - No Shipping Commented-Out Code — Never leave failing lines commented out or deleted in order to make the cell "succeed". Temporary bisection to isolate a bug is a valid debugging step, but the delivered cell MUST execute its intended logic or not at all.
4. Required User Interaction on Unresolvable Failures
When a failure falls into a "STOP" category above, the agent MUST:
- Diagnose: determine the most likely root cause from the error message and context (e.g., "The GCS bucket returned a 403 — this is a permissions issue or the bucket may not exist in this project"). Base the diagnosis on the symptoms you actually observe; do not invent details.
- Report: show the user the exact error message, which cell failed, and the diagnosis.
- Suggest: propose concrete actions the user can take to resolve it
(e.g., "Please verify the bucket exists with
gcloud storage ls gs://foo-bucket/and that your account hasstorage.objectVieweron it"). - Wait: do NOT proceed to subsequent cells. Wait for the user to resolve the issue and explicitly confirm before retrying.
Specialized Notebook Guidance
Refer to the following resources for guidance on specific notebook topics:
1. BigQuery in Notebooks
Use BigFrames magics %%bqsql for BigQuery SQL queries. These cells support
native BigQuery SQL execution and data export to BigFrames dataframes.
[!IMPORTANT]
- Unless specified by the user, always use SQL for querying BigQuery.
- DO NOT use the standard BigQuery Python client library (
google.cloud.bigquery) orpandas.read_gbq.- Mandatory dataframe export: Always provide a dataframe name e.g.
%%bqsql <df_name>. This makes it easy to use results in follow up Python cells.- Verify that
bigframesversion number2.38.0and above is installed in the notebook runtime environment. If it is missing, ask the user if they would like you to upgrade for them.
Example %%bqsql magic usage:
# Initialize BigFrames and load %%bqsql magics
import bigframes
import bigframes.pandas as bpd
%load_ext bigframes
[!CAUTION]
Always use
%load_ext bigframesexactly as shown. Do not load submodules — for example,%load_ext bigframes.magicsor%load_ext bigframes.bigqueryare not valid and must not be used.
[!IMPORTANT]
The
bigframeslibrary must be installed. Determine if bigframes needs to be installed by following @skill:managing-python-dependencies.
%%bqsql df_sample
SELECT * FROM `project.dataset.table` LIMIT 10
Anti-patterns (NEVER DO THESE)
[!CAUTION]
- NO Python SDK for Queries: Do not switch to
client.query(sql).to_dataframe()if SQL fails. Fix the SQL syntax instead.- NO Mixing Logic: Do not put Python code in the same cell as
%%bqsqlmagics.
Working with SQL Results in Python
Magic cells with %%bqsql <df_name> produce a BigQuery DataFrame. In
subsequent cells, you can use <df_name> directly.
[!IMPORTANT]
You MUST use BigFrames for data exploration, manipulation, splitting etc. You MUST use BQML SQL or bigframes.ml for machine learning tasks. You MUST NOT use pandas or Scikit-learn.
BigQuery DataFrame Tips
- Avoid
.to_pandas(): You MUST NOT use.to_pandas()to download the entire dataset into memory. There are some exceptions:- An error message explicitly requests you to use
to_pandas() - You are going to visualize the data, and the visualization library
does not accept BigFrames Dataframe/Series instances. In this case,
reduce the amount of data you are going to download before calling
.to_pandas()
- An error message explicitly requests you to use
- Avoid
read_gbq()for SQL: Do not write SQL queries and execute them withread_gbq(). Use BigFrames Dataframe/Series methods instead. - Use BigFrames ML package for Machine Learning Tasks: Do not use
Scikit-learn or other ML libraries with BigFrames dataframes. Import your
tools/classes from
bigframes.ml. - Stay in the Cloud: Perform data cleaning, transformation, and analysis via BigFrames methods to leverage BigQuery's scale.
- Accessors over UDFs/Lambdas:
- Prefer built-in accessors (e.g.,
df.col.str.*,df.col.dt.*) over remote UDFs. - Do not use lambdas with
Series.map()orDataFrame.apply().
- Prefer built-in accessors (e.g.,
- Schema Verification: Do not assume schema of intermediate outputs. Check
.dtypesafter loading, and usedisplay()with.head()or.peek(). - Visualization: BigFrames Dataframe mostly works directly with Matplotlib, Seaborn, and other plotting libraries. If your attempt didn't work, try using the "plot" accessor. If that didn't work either, you MUST sample or aggregate your data to make it small enough before calling "to_pandas()".
- Model Persistence: To persist a model. use
model.to_gbq(). To load a persisted model, usebpd.read_gbq_model().
2. Machine Learning in Notebooks
Integration with machine learning workflows and best practices. - Guide: Use
@skill:ml-best-practices. - MUST READ WHEN: The task involves machine
learning, training a model, clustering, classification, regression, or
time-series forecasting.
If any "MUST READ WHEN" condition is met, you MUST read the corresponding guide before proceeding.