vtcode-mcp

June 17, 2026 · View on GitHub

Model Context Protocol (MCP) client, connection pooling, and tool discovery for VT Code.

Overview

Layer 1 crate that provides MCP integration, enabling VT Code to connect to MCP servers for extended tool capabilities. Includes connection pooling, tool discovery, and schema validation.

Module Groups

Area	Modules	Description
Client	`client.rs`, `provider.rs`, `rmcp_client.rs`	MCP client implementations
Transport	`rmcp_transport.rs`, `connection_pool.rs`	Transport layer and connection management
Discovery	`tool_discovery.rs`, `tool_discovery_cache.rs`, `schema.rs`	Tool discovery and caching
Types	`types.rs`, `traits.rs`, `errors.rs`, `enhanced_config.rs`	Type definitions and configuration
Utils	`utils.rs`	Utility functions

Key Components

Client

The MCP client handles communication with MCP servers, including request/response handling and protocol negotiation.

Connection Pool

Connection pooling manages multiple MCP server connections efficiently, reducing overhead for repeated requests.

Tool Discovery

Tool discovery automatically finds and catalogs available tools from MCP servers:

tool_discovery.rs — discovers tools from connected servers
tool_discovery_cache.rs — caches discovered tools for performance
schema.rs — tool schema validation

Architecture Notes

cli.rs stays in vtcode-core (depends on crate::cli::input_hardening)
rmcp_client is pub(crate) — not part of the public API
convert_to_rmcp() is pub(crate) — internal JSON bridge
rmcp-reqwest is a renamed reqwest with rustls features — not the same as the workspace reqwest

Configuration

MCP servers are configured through vtcode.toml:

[mcp]
servers = [
  { name = "example", url = "http://localhost:3000" }
]

Environment variables:

DEFAULT_ENV_VARS is platform-conditional (#[cfg(unix)] / #[cfg(windows)])

Dependencies

vtcode-config — MCP configuration
vtcode-commons — shared utilities
vtcode-utility-tool-specs — tool specifications