Marry the power of MCP with the simplicity of http4k

Build secure MCP-compliant servers to integrate Large Language Models with your data and tools using familiar http4k patterns

See the docs

Highlights

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Complete
Protocol

MCP 2025-11-25 + Draft protocols with OAuth & Resource Metadata, passing MCP conformance tests. Full support for Tools, Prompts, Resources, Tasks, Sampling, Elicitation, and more.

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Testable
Design

Pure functions, no side effects. Test Tools, Resources, and MCP Apps fully in-memory - no network, no ports, no flaky CI.

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Type-safe
Tooling

http4k’s powerful Lens system for type-safe tool definitions and capability bindings with compile-time safety.

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MCP
Apps

Server-rendered UI components with the MCP Apps protocol. Dashboards, forms, and visualizations directly in MCP clients. Fully testable.

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Built-in
Observability

OpenTelemetry MCP Semantic Conventions support. Plug into Jaeger, Honeycomb, Datadog - with zero custom instrumentation.

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Machine
Payments

Payment-gated MCP tools and resources with x402 and Machine Payments Protocol (MPP). Protocol-level and tool-level payment filters for automated machine-to-machine commerce.

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Flexible
Transport

HTTP Streaming, SSE, WebSocket, JSON-RPC, and Standard IO transports. Stateful or stateless protocols for desktop and web clients.

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Agent
Connectivity

Build your own AI agents with pure Kotlin MCP protocol clients. Plug any A2A agent straight into Claude Desktop, Cursor, or any MCP client via the provided bridge.

Getting started with MCP in http4k

Step 1 - Define typesafe MCP tools and capabilities using simple, testable functions

Defining MCP tools

Step 2 - Integrate MCP by composing capabilities, with Capability Packs, add security into a lightweight server

Creating an MCP server

Step 3 - Integrate your AI-powered MCP Server or MCP App with Claude Desktop as a standard MCP connector

Using Claude with an MCP server

Step 4 - Access your MCP server from other agents using our pure Kotlin MCP Client

Inter-agent communication
http4k MCP (Model Context Protocol)

Ready to build? Start experimenting with MCP Servers and Apps at the http4k toolbox

License

http4k MCP (Model Context Protocol) is available under the http4k Commercial License. Free usage is granted for qualifying small businesses (<$1m ARR), non-commercial, non-profit, and research activities.

Pricing

All http4k Pro modules are also automatically included as part of the Enterprise Edition. Need bulk developer seats, team licensing, or custom terms? Get in touch and we'll find the right fit - whether that's volume licensing for individual Pro modules or our full Enterprise Edition with LTS support and priority access to all Pro modules.

Let's talk

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