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 agentmods add rules/microsoft/data-formulator/dev-guides-firstgit clone --depth 1 https://github.com/microsoft/data-formulatorWhat 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 | $0.01028 | $0.01028 |
| Opus 5 | $0.00514 | $0.00514 |
| Sonnet 5 | $0.00206 | $0.00206 |
| Haiku 4.5 | $0.00103 | $0.00103 |
Grade A, and why
dev-guides-first 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.
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 — 71 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Dev Guides First
Before Starting Any Development
Before implementing or designing a new feature, module, or significant change, always
read the relevant documents in docs/dev-guides/ to understand existing conventions:
| Guide | When to Read |
|---|---|
docs/dev-guides/1-streaming-protocol.md |
Any work on streaming endpoints or NDJSON protocol |
docs/dev-guides/2-log-sanitization.md |
Any work involving logging, credentials, external services, or DataLoaders |
docs/dev-guides/3-data-loader-development.md |
Any work on ExternalDataLoader, DataConnector, or connector routes |
docs/dev-guides/4-authentication-oidc-tokenstore.md |
Any work on OIDC, TokenStore, AUTH_MODE, or SSO flows |
docs/dev-guides/6-i18n-language-injection.md |
Any work on Agent prompts, Agent routes, backend user-visible messages, or frontend i18n |
docs/dev-guides/7-unified-error-handling.md |
Any work on API errors, frontend API calls, streaming error events, or error tests |
docs/dev-guides/8-path-safety.md |
Any work on backend file access, downloads, Workspace paths, Agent tools, DataLoaders, or sandbox config |
docs/dev-guides/10-agent-knowledge-reasoning-log.md |
Any work on Agent knowledge injection, KnowledgeStore, reasoning logs, or experience distillation |
docs/dev-guides/11-catalog-metadata-sync.md |
Any work on catalog sync, catalog_cache, catalog_annotations, metadata merge, Agent catalog tools, or frontend catalog browsing |
docs/dev-guides/12-sandbox-session.md |
Any work on sandbox execution, Agent tool-calling loops, explore/execute_python code execution, or namespace management |
docs/dev-guides/13-unified-row-limits.md |
Any work on row limits, data loading size caps, frontendRowLimit, MAX_IMPORT_ROWS, or DataLoader size parameter |
docs/dev-guides/14-model-capability-runtime-degradation.md |
Any work on LLM Client calls, Agent LLM invocations, model capability checks, reasoning_effort, or image/vision degradation |
docs/dev-guides/15-dataframe-serialization.md |
Any work on DataFrame→JSON serialization, Agent result rows, DataLoader sample_rows, or table API responses |
.cursor/rules/i18n-no-hardcoded-strings.mdc |
Any work adding or changing user-visible strings in src/ |
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.
- yesterday First seen · 71 lines · 1,028 tokens per session scan A fb84b0b53e2c
dev-guides-first is a cursor rule published in the GitHub repository microsoft/data-formulator (17,048 stars, last pushed 3d ago), licensed MIT. It adds 1,028 tokens to every session, about $0.0051 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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