core

A set of built-in analysis and interaction capabilities for inspecting data and taking actions such as showing a visualization or asking the user a question. The description does not specify a narrower domain.

In plain words
What is it for?
Use it to inspect table schemas, statistics, and sample rows; run Python analysis; load another skill; visualize findings; or ask the user for needed input.
Why use it?
It provides general tools for examining source data and deciding what action to take. The available capabilities depend on the task and the information being inspected.

Skill for Claude CodeCodex

Install

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.

agentmods
npx agentmods add skills/microsoft/data-formulator/core
Any agent
npx skills add microsoft/data-formulator --skill core
Clone the repo
git clone --depth 1 https://github.com/microsoft/data-formulator

Made for: Claude Code, Codex.

Per session 26 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 5,288 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

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.

ModelPer sessionOnce invoked
Fable 5 $0.00026 $0.05288
Opus 5 $0.00013 $0.02644
Sonnet 5 $0.00005 $0.01058
Haiku 4.5 $0.00003 $0.00529

Measured yesterday against content hash af61f68698da, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

core 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 yesterday.

The scan reads SKILL.md. This mod also ships 2 executable files (__init__.py, skill.py), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

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.

py-src/data_formulator/analyst/skills/core/SKILL.md · 315 lines

How it starts

The opening of the file, as written. The whole thing — 315 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Core capabilities

This describes the built-in inspection tools you use to gather data and the always-available actions you take on it. The overall loop, your action budget, and the one-action-per-turn rule are covered in your system instructions — this section is about what each tool and action does and how to use it well.

Tools (for data gathering)

  • execute_python_script(code) — run a general-purpose Python script to inspect data, compute stats, transform tables, or verify assumptions. Its stdout is returned to you (use print()); the script is for your analysis and its output is never shown to the user. pandas, numpy, duckdb, sklearn, scipy are available. Important: each call runs in a fresh namespace — variables do NOT persist between calls, so combine related steps into a single script.
  • inspect_source_data(table_names) — get schema, stats, and sample rows for source tables (cheaper than execute_python_script for basic inspection).
  • load_skill(name) — load a skill's instructions into context so you can use the action it unlocks (see the Skills section of your system instructions).

These are inspection tools — their results come back to you and are never shown to the user; call as many as you need, then take an action or give your final answer.

You analyse data that is already in the workspace. If the user's question requires connected data that isn't present, call load_skill("data-loading") and follow that skill's discovery and immutable proposal workflow in this same conversation. Do not hand off to the standalone Data Loading agent.

The initial context already includes sample rows and statistics for each table. If the data is straightforward, go straight to the action without calling tools. Tool results are returned to you before you act.

Actions

Call an action as a tool call when you want to act on the data. Actions are sequential: take one at a time, then read the result it returns before deciding the next — each action's outcome shapes the next one (the chart you draw next depends on what this one reveals), so emitting several at once would decide the later ones blind. After each result you choose what to do — take another action, or stop. You end your turn by replying with plain text and no action: that is your closing answer when you expect nothing further. When you want the user to reply — a freeform question, a clarification you need before acting, or clickable choices — use the ask_user action instead. It renders a question widget and pauses for their reply, keeping the conversation in the same turn (plain text ends the run, so the user's next message would start fresh without this context).

Read the full file on GitHub · 315 lines

Files

What ships with it

3 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

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.

  1. yesterday First seen · 315 lines · 26 tokens per session scan A af61f68698da

Subscribe to this mod's changes

core is a skill published in the GitHub repository microsoft/data-formulator (17,048 stars, last pushed 3d ago), licensed MIT. It adds 26 tokens to every session and 5,288 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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