A reference guide for OpenTelemetry Transformation Language, or OTTL, used inside the OpenTelemetry Collector. The Collector is a service that receives, changes, filters, and forwards telemetry data.

Use it to rewrite or drop traces, metrics, and logs, decide which traces to keep, and route telemetry to different pipelines.

It helps prevent invalid transformation rules by showing which expressions and functions each Collector component supports.

otel-ottl — Skill for Claude Code by ollygarden

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.

Any agent

npx skills add ollygarden/opentelemetry-agent-skills --skill otel-ottl

Clone the repo

git clone --depth 1 https://github.com/ollygarden/opentelemetry-agent-skills

Made for: Claude Code.

Or install opentelemetry-agent-skills, the plugin that ships this one along with the rest of its 19 skills.

Its marketplace also offers this one on its own, as the plugin otel-ottl — /plugin install otel-ottl after adding the marketplace above.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

README.md

[![agentmods](https://agentmods.dev/badge/skills/ollygarden/opentelemetry-agent-skills/otel-ottl/github.svg)](https://agentmods.dev/skills/ollygarden/opentelemetry-agent-skills/otel-ottl)

Your own site

<a href="https://agentmods.dev/skills/ollygarden/opentelemetry-agent-skills/otel-ottl"><img src="https://agentmods.dev/badge/skills/ollygarden/opentelemetry-agent-skills/otel-ottl/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

Your own site · 80×15

<a href="https://agentmods.dev/skills/ollygarden/opentelemetry-agent-skills/otel-ottl"><img src="https://agentmods.dev/badge/skills/ollygarden/opentelemetry-agent-skills/otel-ottl.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 78 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 1,521 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits

NVIDIA SkillSpector pass 7 Sept 2026

How audits are shown

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.

Model	Per session	Once invoked
Fable 5.1	$0.00078	$0.01521
Opus 5	$0.00039	$0.00760
Sonnet 5	$0.00016	$0.00304
Haiku 4.5	$0.00008	$0.00152

Measured 8d ago against content hash 54ece6c04340, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-12, from the pricing page.

Security

Grade A, and why

otel-ottl 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 8d ago.

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.

skills/otel-ottl/SKILL.md · 95 lines

How it starts

The opening of the file, as written. The whole thing — 95 lines — stays where its author put it; the contents beside it link to each section on GitHub.

OpenTelemetry Transformation Language (OTTL)

OTTL transforms or selects telemetry inside Collector components. This skill is pinned to collector-contrib v0.160.0. Function, path, default, and feature-gate availability varies by release; when the user's version differs, verify against the matching upstream tag.

Workflow

Choose the component. transform rewrites, filter drops, tail_sampling decides whether to retain traces, and routing sends telemetry to pipelines. A component controls its available contexts and functions.
Choose the lowest usable context. Lower contexts can read their parents (for example, a span can read resource.attributes), but parents cannot read children. Use datapoint for point attributes instead of traversing metric.data_points.
Verify every emitted function, then write the statement. Confirm each function's exact identifier and signature in references/functions.md. If an identifier is absent, treat it as unsupported instead of deriving or substituting a plausible name. An editor such as set or delete_key mutates data and may have a where condition. Converters such as ParseJSON and IsMatch return values; they do not mutate.
Set error behavior deliberately. ignore logs statement errors and continues; silent continues without logging; propagate returns the error and can cause the component to drop the payload. In v0.160, transform and filter default to ignore; their stable default-error gates remain registered even though their metadata names v0.159 as the end version. Routing also defaults to ignore while its beta default-error feature gate is enabled. For routing, ignore sends an errored payload to default_pipelines; configure that fallback or the payload is dropped.
Verify end to end. Validate the exact Collector version, then send known telemetry and inspect file-exporter output. Use the telemetrygen recipe.

Read the full file on GitHub · 95 lines

Files

What ships with it

4 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.

8d ago Changed · +2 lines 54ece6c04340
13d ago First seen · 93 lines · 78 tokens per session scan A eababa581e07

Subscribe to this mod's changes

otel-ottl is a skill published in the GitHub repository ollygarden/opentelemetry-agent-skills (98 stars, last pushed yesterday), licensed Apache-2.0. It adds 78 tokens to every session and 1,521 once invoked, about $0.0004 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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