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z9905080

MCP Server for langfuse

by z9905080

MCP Server for langfuse

npm version

A Model Context Protocol (MCP) server implementation for integrating AI assistants with Langfuse workspaces.

Overview

This package provides an MCP server that enables AI assistants to interact with Langfuse workspaces. It allows AI models to:

  • Query LLM Metrics by Time Range

Related MCP server: langfuse-mcp-extended

Installation

# Install from npm
npm install shouting-mcp-langfuse

# Or install globally
npm install -g shouting-mcp-langfuse

You can find the package on npm: shouting-mcp-langfuse

Prerequisites

Before using the server, you need to create a Langfuse project and obtain your project's public and private keys. You can find these keys in the Langfuse dashboard.

  1. set up a Langfuse project

  2. get the public and private keys

  3. set the environment variables

Configuration

The server requires the following environment variables:

  • LANGFUSE_DOMAIN: The Langfuse domain (default: https://api.langfuse.com)

  • LANGFUSE_PUBLIC_KEY: Your Langfuse Project Public Key

  • LANGFUSE_PRIVATE_KEY: Your Langfuse Project Private Key

Usage

Running as a CLI Tool

# Set environment variables
export LANGFUSE_DOMAIN="https://api.langfuse.com"
export LANGFUSE_PUBLIC_KEY="your-public-key"
export LANGFUSE_PRIVATE_KEY="your-private

# Run the server
mcp-server-langfuse

Using in Your Code

import { Server } from "@modelcontextprotocol/sdk/server/index.js";
import { langfuseClient } from "shouting-mcp-langfuse";

// Initialize the server and client
const server = new Server({...});
const langfuseClient = new LangfuseClient(process.env.LANGFUSE_DOMAIN, process.env.LANGFUSE_PUBLIC_KEY, process.env.LANGFUSE_PRIVATE_KEY);

// Register your custom handlers
// ...

Available Tools

The server provides the following langfuse integration tools:

  • getLLMMetricsByTimeRange: Get LLM Metrics by Time Range

License

ISC

Author

shouting.hsiao@gmail.com

Repository

https://github.com/z9905080/mcp-langfuse

Available Tools

1 tool
query_llm_metricsC

Query LLM metrics

ParametersJSON Schema
NameRequiredDescriptionDefault
fromTimestampNoStart timestamp in ISO 8601 format
toTimestampNoEnd timestamp in ISO 8601 format
pageNoPage number (default 1)
limitNolimit (default 100)
traceNameNoTrace name
userIdNoUser ID, it's can filter by user
tagsNoTags
environmentNoEnvironment

TDQS

C2.7/5.0
Behavior2/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

No annotations exist, and the description does not disclose any behavioral traits such as side effects, permissions, rate limits, or data scope. It merely describes a query, which implies a read-only operation but does not explicitly confirm safety or other constraints.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness2/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is extremely short (3 words) but underspecified for a tool with 8 parameters. It lacks necessary detail and is not front-loaded with critical information. Conciseness should not sacrifice completeness.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness2/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the complexity of 8 parameters, no annotations, and no output schema, the description is insufficient. It does not explain what the metrics represent, how results are returned, or any context for interpreting the data. The agent is left without enough information to effectively use the tool.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, so the baseline is 3. The description adds no meaning beyond the schema's parameter descriptions. It does not explain how to use parameters together or provide context that helps the agent understand parameter relationships.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

Description states 'Query LLM metrics' which clearly identifies the verb and resource. It is a simple, direct statement of the tool's purpose, though it lacks specificity about which metrics. It is not a tautology and distinguishes the tool as a query operation.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines2/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

No guidance provided on when to use this tool, what scenarios it is suited for, or any alternatives. The description gives no context for appropriate usage, leaving the agent without decision-making information.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

Tool Schema Changelog

Recent tool additions, removals, and schema changes observed during successful MCP inspections.

  1. 1 tool update
    • First observedquery_llm_metrics

TDQS

C2.8/5.0

Scored across 1 tool

Disambiguation5/5

With only one tool, there is no possibility of confusion or overlap with other tools. The tool's purpose is clear and unambiguous.

Naming Consistency5/5

The single tool uses a clear snake_case naming convention. Although there are no other tools to compare, the naming is consistent within itself.

Tool Count1/5

A server named 'MCP Server for langfuse' with only one tool is severely undersized. Langfuse is a comprehensive LLM observability platform expecting tools for traces, scores, sessions, etc., not just metrics queries.

Completeness1/5

The server lacks any tools for creating, updating, or deleting resources, and does not cover common operations like managing traces or observations. It is severely incomplete for its stated domain.

Maintenance

ActivityInactive
ResponsivenessNo issues

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