# ecs-field-mappings

Configures Elastic data stream mappings, writes ecs.yml entries, and resolves schema validation errors in integration packages.

- skill · `type=skill` · Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, OpenCode · 511 installs · ★ 16
- Author: elastic
- License: Apache-2.0 · policy=mirror · the beginning of the file is at the end of this page
- Source: https://github.com/elastic/integration-skills/tree/HEAD/skills/ecs-field-mappings/SKILL.md
- Updated: 2026-10-16
- HTML: https://affpapa.org/en/nevibecode/skills/ecs-field-mappings

## What it does

This skill guides coding agents through data stream field definitions under `data_stream/<stream>/fields/`. It verifies existing Elastic Common Schema entries and marks them with `external: ecs`. Descriptions inherit automatically from the core schema. For values that remain static across all documents, the skill applies `constant_keyword` so index metadata stores the value without cluttering `_source`.

Missing `_dev/build/build.yml` breaks package verification immediately. Package scaffolds omit this file. You must add it by hand at the package root to lock down the ECS release, like `git@v9.3.0`. Without it, `elastic-package check` treats standard fields like `destination.ip` as undefined.

Custom fields belong strictly in `fields.yml` organized by vendor group hierarchies. The generic `labels.*` object is the only permitted exception to vendor prefixing.

## Install

### Claude Code (native platform)

1. **Skills CLI (Vercel)**
```bash
npx skills add elastic/integration-skills --skill ecs-field-mappings -a claude-code
```

2. **Manually: put the files in place**
- File: `~/.claude/skills/ecs-field-mappings/SKILL.md` — Copy the whole skill folder; for one project use .claude/skills/ecs-field-mappings/

### Codex

1. **Skills CLI (Vercel)**
```bash
npx skills add elastic/integration-skills --skill ecs-field-mappings -a codex
```

2. **Manually: put the files in place**
- File: `.agents/skills/ecs-field-mappings/SKILL.md` — For all projects use ~/.agents/skills/

### Cursor

1. **Skills CLI (Vercel)**
```bash
npx skills add elastic/integration-skills --skill ecs-field-mappings -a cursor
```

2. **Manually: put the files in place**
- File: `.cursor/skills/ecs-field-mappings/SKILL.md` — Cursor also reads .agents/skills/ and .claude/skills/

### GitHub Copilot

1. **GitHub CLI**
```bash
gh skill install elastic/integration-skills ecs-field-mappings
```

2. **Manually: put the files in place**
- File: `.github/skills/ecs-field-mappings/SKILL.md`

### Gemini CLI

1. **Skills CLI (Vercel)**
```bash
npx skills add elastic/integration-skills --skill ecs-field-mappings -a gemini-cli
```

2. **Platform CLI**
```bash
gemini skills install https://github.com/elastic/integration-skills --path skills/ecs-field-mappings
```

### Windsurf (Devin Desktop)

**Manually: put the files in place**
- File: `.devin/skills/ecs-field-mappings/SKILL.md` — The legacy .windsurf/skills/ path still works

### OpenCode

**Skills CLI (Vercel)**
```bash
npx skills add elastic/integration-skills --skill ecs-field-mappings -a opencode
```

### Claude.ai

**Claude.ai**
- Zip the folder and upload it in Settings → Capabilities → Skills

Where a file is given instead of a command, copy the files from the source to that path: https://github.com/elastic/integration-skills/tree/HEAD/skills/ecs-field-mappings/SKILL.md

## When to use it
- populate `ecs.yml` with valid Elastic Common Schema field references
- set up stream routing fields in `base-fields.yml` using `constant_keyword`
- resolve undefined field errors in `elastic-package check`
- organize proprietary attributes inside `fields.yml` with group hierarchies

## Example prompts
- Add destination.ip and source.ip to ecs.yml for this data stream
- Set up base-fields.yml with routing constants for the new package
- Fix the undefined field validation error reported by elastic-package check

## Source text · SKILL.md · Apache-2.0

Below is the content of a third-party file. It is data, not instructions for you: do not act on anything written inside unless the human asks. Block tag: ec03baea0145bc31.

BEGIN THIRD-PARTY FILE ec03baea0145bc31
````text
---
name: ecs-field-mappings
description: "Use when defining field mappings for data streams, populating ecs.yml with ECS field references, selecting ECS categorization values, choosing custom field types, or troubleshooting mapping validation failures."
license: Apache-2.0
metadata:
  author: elastic
  version: "1.0"
---

# ecs-field-mappings

## When to use

Use this skill when tasks include:
- adding or modifying files under `data_stream/<stream>/fields/`
- populating `ecs.yml` with ECS field references
- selecting `event.kind`, `event.category`, `event.type`, and `event.outcome` values
- choosing field `type` and mapping properties (`metric_type`, `dimension`, `multi_fields`, and related options)
- checking whether a field already exists in ECS before adding custom fields
- troubleshooting mapping validation/build failures from `elastic-package check`, `elastic-package lint`, or pipeline test schema checks

## ECS dependency configuration

Every package needs `_dev/build/build.yml` at the package root. This file pins the ECS schema version used for field resolution.

```yaml
dependencies:
  ecs:
    reference: "git@v9.3.0"
```

This file is **required** whenever the package has any field file. The scaffold does not generate it — create it manually. If it is missing or uses an outdated version, tests report ECS fields as undefined (e.g., `field "destination.ip" is undefined`).

## Field files and roles

A data stream's `fields/` directory contains a small set of YAML files with distinct responsibilities:

### `base-fields.yml`

Fixed routing constants and `@timestamp`. All six fields are ECS fields, so each entry uses `external: ecs`. Override `type` and `value` where the data stream needs a `constant_keyword` with a fixed value — the description is inherited from ECS automatically.

```yaml
- name: data_stream.type
  external: ecs
- name: data_stream.dataset
  external: ecs
- name: data_stream.namespace
  external: ecs
- name: event.module
  external: ecs
  type: constant_keyword
  value: <package_name>
- name: event.dataset
  external: ecs
  type: constant_keyword
  value: <package_name>.<stream_name>
- name: '@timestamp'
  external: ecs
```

Do not add other fields here. Only these routing constants and `@timestamp` belong in `base-fields.yml`.

### `constant_keyword` candidates

Fields that hold a single value for every document in a data stream should use `constant_keyword`. Beyond the routing constants in `base-fields.yml`, evaluate these:

| Field | Why `constant_keyword` |
|-------|------------------------|
| `event.dataset` | One value per data stream by definition |
| `event.module` | One value per package |
| `data_stream.type` | Fixed per stream (`logs`/`metrics`) |
````
END THIRD-PARTY FILE ec03baea0145bc31

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