Discover tools at runtime with AWS Agent Registry

AWS has introduced Agent Registry, a managed service for cataloging and discovering Model Context Protocol servers, agents and agent skills, so orchestrators can find tools at runtime instead of hardcoding them.

• The post argues that hardcoded tools work for a handful but degrade at a few dozen and become unmanageable beyond that, as enterprise systems expose hundreds of internal APIs for pricing, support, orders, inventory and customer data.
• Publishers register protocol-specific descriptors and searchable descriptions, and an orchestrator can search approved, discoverable records and use the returned endpoint and descriptor content to construct a client.
• Registry search results do not return the capability's invocation credentials or authentication scheme, so the application must obtain and apply credentials through a separate, trusted configuration path.
• A refactored Python sample demonstrates a Discover, Instantiate, Execute loop that deploys an order-management MCP server through Amazon Bedrock AgentCore Gateway, two agent-to-agent agents on AgentCore runtime, a Registry and an orchestrator.
• An ephemeral inner agent is built with only the dynamically discovered tools, and after the turn finishes the inner agent and its clients are torn down, so the next request gets a fresh search and a fresh tool set.
• Three demo scenarios exercise the loop: an MCP-only order status call, a chained MCP and A2A pricing and discounts call, and a semantic match for return and refund where those words do not appear in the matched agent's name.