Agent MCP Directory

MCP, A2A and WebMCP by job

Choose the surface by the job: tools on a server, delegation to another agent, or actions on a live page. A table below sets the three side by side. Use MCP for tools and data behind an API, A2A when another agent should take a task and WebMCP when a user is on the page and the agent acts there.

Steps

  1. Tools and data behind an API: MCP.
  2. Another agent should take a task: A2A Agent Card.
  3. A user is on the page and the agent acts there: WebMCP.

What the sources say

  • MCP standard transports are stdio and Streamable HTTP. (modelcontextprotocol.io, read 4 November 2026)
  • A2A 1.0.0 binds to JSON-RPC, gRPC or HTTP+JSON and publishes /.well-known/agent-card.json. (a2a-protocol.org, read 4 November 2026)
  • WebMCP tools live in the page and are reached through document.modelContext. (github.com, read 4 November 2026)
  • MCP and A2A are both projects of the Agentic AI Foundation since A2A joined on 27 Aug 2026. (a2a-protocol.org, dated 27 August 2026, read 4 November 2026)
  • Kong AI Gateway reports OpenTelemetry metrics for AI, MCP and A2A traffic side by side. (developer.konghq.com, read 4 November 2026)

The three side by side

StandardWhat it isStatus and version
Model Context ProtocolA JSON-RPC 2.0 protocol between hosts, clients and servers; servers offer tools, resources and prompts, and clients may offer elicitation.Current revision 2026-07-28 (released 28 Jul 2026); prior revision 2025-11-25. Registry in preview with API v0.1 frozen since 24 Oct 2025.
Agent2AgentA protocol for agents to discover each other through an Agent Card and exchange tasks and messages.Specification 1.0.0 is the latest release; joined the Agentic AI Foundation on 27 Aug 2026.
WebMCPA browser API that lets a page register JavaScript functions as tools, with descriptions and schemas, that an in-browser agent can call.Draft specification; Chrome and Edge test it in an origin trial, Brave behind a flag, no Firefox or Safari implementation (nekuda FAQ, October 2026).

Pairwise: MCP vs A2A, MCP vs WebMCP and WebMCP vs agents.json.