derivation-flatten-array SKILL.md skillA
derivation-flatten-array from estuary/agent-skills is an agent skill: a SKILL.md folder an AI agent loads when a task calls for it.
mdr add estuary/agent-skills/derivation-flatten-array@git:20260707.6b608bfPins git:20260707.6b608bf in mdr.lock. Pin the fingerprint instead.
- Audit grade
- A, 17 of 17 checks passed
- Kind
- SKILL.md skill
- Repository
- estuary/agent-skills
- Path
skills/derivation-flatten-array/SKILL.md- Versions recorded
- 1
- Latest version
- git:20260707.6b608bf, committed Jul 7, 2026
- Size
- 11,148 bytes
- Repository stars
- 7
- License
- Apache-2.0
Create an Estuary derivation that flattens a nested array into one output document per array element. Use for normalising nested JSON, exploding line items, unpacking tags, or producing one-row-per-item tables from arrays. Derivations add complexity and cost — confirm the user wants a derivation before reaching for this (some destinations can `UNNEST` server-side without one). Use when user says "flatten-array derivation", "derivation to explode an array", "transformation to unnest…
Collected from public GitHub. Every version is saved exactly as it was and never changes. Install it at an exact version with the mdr tool, and every file is checked before it reaches your agent. The main file is checked against the SHA-256 fingerprint recorded here, and the others against the fingerprints GitHub keeps for its source commit. The automatic checks below grade the latest version, and the same checks always give the same file the same grade.
What the file says
# derivation-flatten-array
Stateless Estuary derivation that emits many output documents from a single source document by iterating over a nested array.
**Prereq:** read `derivation-basics` first for concepts, project layout, workflow, and language choice.
**Docs:** https://docs.estuary.dev/guides/flatten-array/ — the official TypeScript walkthrough for this exact pattern. Read it alongside this skill.
## When to use this over alternatives
- **Normalising nested JSON:** `{order_id, line_items: [...]}` → one doc per line item
- **Exploding tags/categories:** `{article_id, tags: ["a", "b", "c"]}` → one doc per tag
- **Unpacking array columns** from source databases for analytics
- **Preparing data for systems that prefer normalised 1-row-per-item tables**
If the array isn't in the source document itself (e.g., you need to join across collections to assemble it), use `derivation-join-collections`. If you just need to keep the array intact but change how it's materialised (e.g., MongoDB `flow_document`), you don't need a derivation at all.
## Canonical Example — TypeScript (recommended)
…Read the whole file at its exact version.
How to install
mdr add estuary/agent-skills/derivation-flatten-array@sha256:7b8d1af9d549b297The line at the top of this page pins the label git:20260707.6b608bf, which is what most people want. This one pins the sha256 fingerprint of the contents instead, so it survives a label being moved. Either way the exact version is written to mdr.lock, and mdr install downloads and checks those contents again, so it installs them exactly or stops with an error.
[](https://markdownregistry.com/a/art_o2j5hkd56fwhw5bf)
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Versions
The registry has recorded 1 version of this file, committed on Jul 7, 2026.
Audit of the latest version
- pass: Frontmatter block present
- pass: Frontmatter declares a name
- pass: Frontmatter declares a description
- pass: Size between 200 bytes and 200 KB (11148 bytes)
- pass: No zero-width or bidi control characters
- pass: No instruction hidden inside an HTML comment
- pass: No link to an exfiltration or paste host
- pass: No credential-shaped string
- pass: No instruction to send local credentials anywhere
- pass: No text hidden with inline styles
- pass: No prompt-injection phrasing
- pass: No curl or wget piped into a shell
- pass: No recursive delete of root, home or parent
- pass: No instruction to read or print local credentials
- pass: No base64 blob over 200 characters
- pass: No link to a raw IP address
- pass: No script tag
Source
estuary/agent-skills · 7 stars · license Apache-2.0 · pushed 2026-11-04 · branch main
API
GET https://markdownregistry.com/api/v1/artifacts/art_o2j5hkd56fwhw5bf GET https://markdownregistry.com/api/v1/resolve?ref=estuary/agent-skills/derivation-flatten-array GET https://markdownregistry.com/api/v1/blob/7b8d1af9d549b297d7a2866415bbf7a9e9f1e644e652d26f64954d475c201e11
Your AI assistant does the legwork. You hear about the deals worth your word. Hand yours the standing instructions at modelranch.com and it joins the network that reads files like this one.
Guides: the SKILL.md format and its required fields · what to check before you install a skill · how to pin a skill to an exact version · where to find agent skills · keeping a team on the same skills · which agent file does what.