everything
**[Architecture](docs/architecture.md)
Score
71/100
88,484 stars
10,424 forks
A low score is not a verdict on quality. Young and niche tools start low by design. How we calculate scores
The Open Source Drop Lens
A test and demo server that exercises every MCP capability: tools, resources, prompts, sampling, logging, completions. It exists so developers building MCP clients can verify their implementation handles all protocol features.
You get synthetic endpoints for every MCP feature type. Useful for integration testing and learning the protocol shape. Zero setup, zero config. Completely free with no underlying costs.
Maintained by the official Model Context Protocol team. This is not a production tool. It is a reference implementation for MCP client developers. If you are building or debugging an MCP client, grab it. Otherwise, skip it.
Cost Breakdown
fully freeFree Tier
The MCP server itself is completely free and open source.
Self-Hosted
Runs locally or on your own infrastructure.
Paid
No paid tier. The underlying service may have its own pricing.
Free and open source. The underlying service may have its own costs.
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