List all Langfuse projects accessible with the current API key.

List all organizations.

Find a project by name or create it if it doesn't exist.

Args: name: Project name to find or create. org_id: Organization ID to create in if not found (get from list_organizations).

Record that a local repo/path uses a specific Langfuse project.

Args: path: Absolute path to the local project/repo. project_id: Langfuse project ID to associate with this path. project_name: Optional human-readable project name for reference.

Look up which Langfuse project a local repo/path is mapped to. Walks up the directory tree to find the nearest match.

Args: path: Absolute path to look up (usually the current working directory).

List all local repo → Langfuse project mappings.

Create a new project inside an organization.

Args: name: Display name for the project. org_id: The organization ID to create the project in (get from list_organizations).

Create a new API key pair (pk/sk) for a project.

Returns the secret key — store it immediately, it is not shown again.

Args: project_id: The project ID to create the key for. note: Optional label for the key.

List API keys for a project.

Args: project_id: The project ID.

Delete an API key by its ID.

Args: key_id: The API key ID to delete (get from list_api_keys).

List traces with optional filters.

Args: limit: Number of results (max 100). page: Page number (1-based). user_id: Filter by user ID. session_id: Filter by session ID. name: Filter by trace name. tags: Filter by tags.

Get full details of a trace including observations.

Args: trace_id: The trace ID.

List sessions.

Args: limit: Number of results (max 100). page: Page number (1-based).

List scores with optional filters.

Args: limit: Number of results (max 100). page: Page number (1-based). trace_id: Filter by trace ID. user_id: Filter by user ID. name: Filter by score name.

Create a score on a trace or observation.

Args: trace_id: The trace to score. name: Score name (e.g. "quality", "faithfulness"). value: Numeric value (or 0/1 for BOOLEAN, category index for CATEGORICAL). observation_id: Optionally attach score to a specific observation. comment: Optional comment. data_type: NUMERIC | BOOLEAN | CATEGORICAL.

List observations (spans, generations, events).

Args: trace_id: Filter by trace ID. limit: Number of results (max 100). page: Page number (1-based). obs_type: Filter by type: SPAN | GENERATION | EVENT.

List datasets.

Args: limit: Number of results. page: Page number.

Get a dataset and its items.

Args: dataset_name: The dataset name.

List prompts in the prompt library.

Args: limit: Number of results. page: Page number. name: Filter by name.

Get a prompt by name, optionally pinned to a version or label.

Args: prompt_name: The prompt name. version: Specific version number. label: Label (e.g. "production", "latest").