Everything you need to build, debug, and monetise AI agents on the JVM.

The complete http4k toolkit for AI agent systems. MCP servers and Apps, A2A agent interop, machine payments, and full observability - all testable in-memory with familiar http4k patterns.

See the docs

Highlights

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MCP
SDK

Full MCP protocol support - Tools, Prompts, Resources, Tasks, Sampling, Elicitation, OAuth. MCP Apps for server-rendered UI in Claude Desktop and other MCP clients.

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Agent2Agent
Protocol

Full A2A spec with both JSON-RPC and REST bindings. Agent Cards, Tasks, Streaming, Push Notifications, and multi-turn conversations for interoperable multi-agent systems.

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Wiretap

Intercept JUnit extension with HTML reports, sequence diagrams, and living docs. Wiretap Console for live traffic monitoring, chaos engineering, and MCP debugging.

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Machine
Payments

X402 and MPP support for both HTTP and MCP. Payment-gated endpoints, tools, and resources. Client and server filters with automatic 402 handling.

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Agent
Connectivity

MCP and A2A clients with full streaming support. Plug any A2A agent straight into Claude Desktop, Cursor, or any MCP client via the provided bridge. Test in-memory with no network, no ports, no flaky CI.

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Multi-Transport

HTTP Streaming, SSE, WebSocket, and Standard IO for MCP. JSON-RPC and REST for A2A. Deploy the same logic over any transport.

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Observability

OpenTelemetry tracing across MCP and A2A with semantic conventions. Plug into Jaeger, Honeycomb, Datadog - zero custom instrumentation.

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Security &
Multi-tenancy

OAuth, API keys, mTLS, and OpenID Connect security schemes. First-class tenant isolation across tasks, storage, and routing.

Build a complete AI agent system

Define MCP tools and A2A Agent Cards with type-safe, testable functions - the building blocks of your agent system.

Add Wiretap Intercept to your tests - one annotation for full OpenTelemetry capture with HTML reports. Use @RegisterExtension for multi-agent sequence diagrams.

Compose into production servers with security, payments, and observability. Wrap with Wiretap() for a full runtime console.

Connect agents via A2A for multi-agent collaboration. Gate premium tools with X402/MPP payments. Debug with Claude via Wiretap’s MCP server.

License

http4k Agent Pack 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.

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