MCP Client Capabilities

This package strives to be the most up-to-date database of all Model Context Protocol (MCP) clients and their capabilities, to enable MCP servers understand what features an MCP client supports and how to respond to it in order to provide the best user and agent experience. Unfortunately, the MCP protocol capability negotiation during the initial handshake is not sufficient for that—see Background bellow for details.

In other words, this package is the programmatic version of the community MCP clients table.

How it works

This package provides a JSON file called mcp-clients.json that lists all known MCP clients, their metadata and capabilities. It's a single JSON file to make it easy for multiple programming languages to access the data while enabling TypeScript type safety for the NPM package.

The JSON file contains an object where keys are client names and values an object with information about the MCP client:

{
  // Client name corresponds to `params.clientInfo.name` from the MCP client's `initialize` request, e.g. "ExampleClient"
  "<client-name>": {

    // Display name of the MCP client, e.g. "Example Client"
    title: string,
    
    // URL to the homepage of the client
    url: string,
    
    // Corresponds to `params.protocolVersion` from the MCP client's `initialize` request, e.g. "2024-11-05"
    protocolVersion: string,

    // Present if the client supports accessing server resources,
    // whether it can handle their dynamic changes, and whether it can subscribe to resource updates
    resources?: { listChanged?: boolean, subscribe?: boolean },

    // Present if the client supports accessing server prompts,
    // and whether it can handle their dynamic changes
    prompts?: { listChanged?: boolean },

    // Present if the client supports accessing server tools,
    // and whether it can handle their dynamic changes.        
    tools?: { listChanged?: boolean },

    // Present if the client supports elicitation from the server.    
    elicitation?: object,
    
    // Present if the client supports sampling from an LLM.
    sampling?: object,

    // Present if the client supports listing its roots,
    // and whether it can notify the server about their dynamic changes        
    roots?: { listChanged?: boolean },

    // Present if the client can handle server's argument autocompletion suggestions.         
    completions?: object,
    
    // Present if the client supports reading log messages from the server.        
    logging?: object,
  },
  "<client-name-2>": { ... },
  ...
}

Note that the client object is inspired by MCP's ClientCapabilites and ServerCapabilites objects, and the respective field types are compatible. Additional fields might be added in the future.

IMPORTANT: MCP servers must always prioritize the information received from the MCP client's initalize request via the params.capabilities field (of type ClientCapabilites) to the capabilities information provided by this package, as it will always be more accurate!

Client versioning