schema-null-defaults SKILL.md skillA
schema-null-defaults 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/schema-null-defaults@git:20260707.049f6aePins git:20260707.049f6ae 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/schema-null-defaults/SKILL.md- Versions recorded
- 1
- Latest version
- git:20260707.049f6ae, committed Jul 7, 2026
- Size
- 5,506 bytes
- Repository stars
- 7
- License
- Apache-2.0
Handle NULL values and set default values for missing fields in collections and materializations. Use when fields need defaults, nullable primary key errors occur, or source data has gaps. Use when user says "NULL values", "default value", "missing field", "nullable primary key error", or "fill in missing data".
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
# Handle NULLs and Default Values Handle NULL values and set default values for missing fields in materializations. **Docs:** https://docs.estuary.dev/concepts/schemas/#default-annotations ## When to Use - Need to provide default values for missing/optional fields - Handling nullable primary key errors in materializations (`cannot materialize collection with nullable key field unless it has a default value annotation`) - Ensuring consistent values when source data has gaps ## Prerequisites - Existing collection to modify - `flowctl` authenticated ## Key Concepts - `default` applies only to **missing** fields, not to explicit `null` values. A field present with `null` stays `null`. - `default` is read by materializations only — captures and derivations ignore it. Add defaults to the readSchema so auto-discover (which only touches writeSchema/connector-schema) can't overwrite them. ## Procedure ### Step 1: Pull Collection Specs ```bash flowctl catalog pull-specs --name <tenant>/<collection-name> ``` ### Step 2: Identify the Read Schema Find the read schema file (e.g., `collection.read.schema.yaml`). Typical structure for collections using schema inference: ```yaml …
Read the whole file at its exact version.
How to install
mdr add estuary/agent-skills/schema-null-defaults@sha256:8614218ba148beceThe line at the top of this page pins the label git:20260707.049f6ae, 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_acgc4xupityvzdns)
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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
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- 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_acgc4xupityvzdns GET https://markdownregistry.com/api/v1/resolve?ref=estuary/agent-skills/schema-null-defaults GET https://markdownregistry.com/api/v1/blob/8614218ba148becec5f4353bf037d882271eae979f19922c24c5aa925765d594
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.