langfuse

name

langfuse

description

Interact with Langfuse and access its documentation. Use when needing to (1) query or modify Langfuse data programmatically via the CLI — traces, prompts, datasets, scores, sessions, and any other API resource, (2) look up Langfuse documentation, concepts, integration guides, or SDK usage, or (3) understand how any Langfuse feature works. This skill covers CLI-based API access (via npx) and multiple documentation retrieval methods.

Langfuse

Two core capabilities: programmatic API access via the Langfuse CLI, and documentation retrieval via llms.txt, page fetching, and search.

1. Langfuse API via CLI

Use the langfuse-cli to interact with the full Langfuse REST API from the command line. Run via npx (no install required):

npx langfuse-cli api <resource> <action>

Quick Start

# Discover all available resources
npx langfuse-cli api __schema

# List actions for a resource
npx langfuse-cli api <resource> --help

# Show args/options for a specific action
npx langfuse-cli api <resource> <action> --help

Credentials

Set environment variables before making calls:

export LANGFUSE_PUBLIC_KEY=pk-lf-...
export LANGFUSE_SECRET_KEY=sk-lf-...
export LANGFUSE_HOST=https://cloud.langfuse.com  # optional, default is EU

If not set, ask the user for their API keys (found in Langfuse UI → Settings → API Keys) and which host they use (cloud.langfuse.com, us.cloud.langfuse.com, or self-hosted URL).

Detailed CLI Reference

For common workflows, tips, and full usage patterns, see references/cli.md.

2. Langfuse Documentation

Three methods to access Langfuse docs, in order of preference:

2a. Documentation Index (llms.txt)

Fetch the full index of all documentation pages:

curl -s https://langfuse.com/llms.txt

Returns a structured list of every doc page with titles and URLs. Use this to discover the right page for a topic, then fetch that page directly.

Alternatively, you can start on https://langfuse.com/docs and explore the site to find the page you need.

2b. Fetch Individual Pages as Markdown

Any page listed in llms.txt can be fetched as markdown by appending .md to its path or by using Accept: text/markdown in the request headers. Use this when you know which page contains the information needed. Returns clean markdown with code examples and configuration details.

curl -s "https://langfuse.com/docs/observability/overview.md"
curl -s "https://langfuse.com/docs/observability/overview" -H "Accept: text/markdown"

2c. Search Documentation

When you need to find information across all docs and github issues/discussions without knowing the specific page:

curl -s "https://langfuse.com/api/search-docs?query=<url-encoded-query>"

Example:

curl -s "https://langfuse.com/api/search-docs?query=How+do+I+trace+LangGraph+agents"

Returns a JSON response with:

• query: the original query
• answer: a JSON string containing an array of matching documents, each with:
  • url: link to the doc page
  • title: page title
  • source.content: array of relevant text excerpts from the page

Search is a great fallback if you cannot find the relevant pages or need more context. Especially useful when debugging issues as all GitHub Issues and Discussions are also indexed. Responses can be large — extract only the relevant portions.

Documentation Workflow

1. Start with llms.txt to orient — scan for relevant page titles
2. Fetch specific pages when you identify the right one
3. Fall back to search when the topic is unclear and you want more context