Langfuse API

Name: langfuse-api
Rating: 78
Author: langfuse

Help users interact with Langfuse via the REST API.

When to Use

•User wants to query or export traces
•User wants to manage prompts programmatically
•User wants to create/update datasets or dataset items
•User wants to fetch or create scores
•User wants to manage projects or API keys
•Any other Langfuse API interaction

Workflow

1. Check Credentials

Before making any API call, verify credentials are available:

bash

echo $LANGFUSE_PUBLIC_KEY   # pk-...
echo $LANGFUSE_SECRET_KEY   # sk-...
echo $LANGFUSE_HOST         # https://cloud.langfuse.com (or self-hosted/EU/US URL)

If not set, ask user:

•"I need your Langfuse API credentials. You can find them in Settings → API Keys in the Langfuse UI."
•"Which Langfuse host are you using? (cloud.langfuse.com, us.cloud.langfuse.com, eu.cloud.langfuse.com, or self-hosted URL)"

2. Fetch Fresh API Reference

Always fetch the current API reference before making calls. The API may have new endpoints or changed parameters.

Fetch: https://api.reference.langfuse.com

Look for the specific endpoint needed for the user's request. The reference contains:

•All available endpoints
•Required and optional parameters
•Request/response schemas
•Authentication details

3. Make the API Call

Authentication: Basic Auth with LANGFUSE_PUBLIC_KEY as username and LANGFUSE_SECRET_KEY as password.

Base URL: {LANGFUSE_HOST}/api/public

Example:

bash

curl -X GET "${LANGFUSE_HOST}/api/public/traces" \
  -u "${LANGFUSE_PUBLIC_KEY}:${LANGFUSE_SECRET_KEY}" \
  -H "Content-Type: application/json"

4. Handle Pagination

Many endpoints return paginated results. Check for:

•page and limit parameters
•meta.totalItems and meta.totalPages in response
•Iterate if user needs all results

Common Use Cases

User Request	Endpoint to Look Up
"Get my recent traces"	GET /traces
"Export traces from last week"	GET /traces with date filters
"Fetch a specific prompt"	GET /prompts/{name}
"Create a dataset"	POST /datasets
"Add items to dataset"	POST /dataset-items
"Get scores for a trace"	GET /scores with traceId filter
"List all prompts"	GET /prompts

Important Notes

•Always fetch fresh docs - Don't rely on cached knowledge of the API
•Check rate limits - The API has rate limits; handle 429 responses
•Validate responses - Check for errors before processing data
•Large exports - For bulk data, use pagination and consider streaming to file

OpenAPI Spec

For programmatic access or generating types:

code

https://cloud.langfuse.com/generated/api/openapi.yml