05
Protocols & standards
MCP connects to tools. A2A connects to agents.
Verified Complementary, not competing — together they replace fragmented "glue-code" with a standard foundation. MCP cuts integration from M×N to M+N.
topology · agent ⇄ tools (mcp, vertical) · agent ⇄ agent (a2a, horizontal)
Verified
MCP won the tool-protocol debate.
~97M monthly SDK downloads by early 2026; native support in OpenAI, Google, Microsoft, AWS. Created by Anthropic Nov 2024. Now under the Linux Foundation.
Reported
MCP architecture: host → client → server; four primitives.
Tools, Resources, Prompts, Sampling. Transports: stdio, HTTP+SSE, Streamable HTTP. Originally lacked auth — later embedded OAuth 2.1.
Reported
Security is the live concern.
An Endor Labs scan of 2,614 MCP servers found 82% prone to path traversal, 67% to code injection. Combining A2A+MCP compounds prompt-injection, RCE and semantic-interoperability risks.