MCP Server

A Model Context Protocol (MCP) server for querying Weights & Biases Weave traces. This server allows a MCP Client to:

• query W&B Weave traces
• write text and charts to W&B Reports

Available tools

• query_weave_traces_tool: Queries Weave traces with powerful filtering, sorting, and pagination options. Returns either complete trace data or just metadata to avoid overwhelming the LLM context window.

• count_weave_traces_tool: Efficiently counts Weave traces matching given filters without returning the trace data. Returns both total trace count and root traces count to understand project scope before querying.

• create_wandb_report_tool: Creates a new W&B Report with markdown text and HTML-rendered visualizations. Provides a permanent, shareable document for saving analysis findings and generated charts.

Usage

Ensure you specify the W&B Entity and W&B Project to the LLM/MCP Client.

Example query for Claude Desktop:

how many openai.chat traces in the wandb-applied-ai-team/mcp-tests weave project? plot the most recent 5 traces over time and save to a report

Installation

uv venv && source .venv/bin/activate
uv pip install -e .

Configuration

1. Create a .env file in the root directory with your Weights & Biases API key:

WANDB_API_KEY=your_api_key_here

Running the Server

Run the server using:

uv run src/mcp_server/server.py

Client Setup

Claude Desktop

    "mcpServers": {
        "weights_and_biases": {
        "command": "uv",
        "args": [
            "--directory",
            "/ABSOLUTE/PATH/TO/PROJECT",
            "run",
            "src/server.py"
        ]
        }
    }