Creating an LLM agent newsroom with A2A protocol and MCP in Elasticsearch: Part II

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A2A and MCP: the code in action

This is the companion piece to the article “Creating an LLM Agent newsroom with A2A protocol and MCP in Elasticsearch!”, which explained the benefits of implementing both A2A and MCP architectures within the same agent to truly reap the unique benefits of both frameworks. A repository is available should you wish to run the demo on your own.

Let's walk through how our newsroom agents collaborate using both A2A and MCP to produce a news article. The accompanying repository to see the agents in action may be found here.

Step 1: Story assignment

The News Chief (acting as the client) assigns a story:

Step 2: Reporter requests research

The Reporter Agent recognizes it needs background information and delegates to the Researcher Agent via A2A:

Step 3: Reporter requests historical context from Archive Agent

The Reporter Agent recognizes that historical context would strengthen the story. It delegates to the Archive Agent (powered by Elastic's A2A Agent) via A2A to search the newsroom's Elasticsearch-powered article archive:

Step 4: Archive Agent uses Elastic A2A Agent with MCP

The Archive Agent uses Elastic's A2A Agent, which in turn uses MCP to access Elasticsearch tools. This demonstrates the hybrid architecture where A2A enables agent collaboration while MCP provides tool access:

The Archive Agent receives comprehensive historical data from Elastic's A2A Agent and returns it to the Reporter:

This step demonstrates how Elastic's A2A Agent integrates into the newsroom workflow. The Archive Agent (a newsroom-specific agent) coordinates with Elastic's A2A Agent (a third-party specialist) to leverage Elasticsearch's powerful search and analytics capabilities. Elastic's agent uses MCP internally to access Elasticsearch tools, showing the clean separation between agent coordination (A2A) and tool access (MCP).

Step 5: Researcher uses MCP servers

The Researcher Agent accesses multiple MCP servers to gather information:

Step 6: Researcher returns data to Reporter

The Researcher Agent sends comprehensive research back via A2A:

Step 7: Reporter writes article

The Reporter Agent uses the research data and its own LLM capabilities to write the article. During writing, the Reporter uses the MCP servers for style and templates:

Step 8: low confidence triggers Re-Research

The Reporter Agent evaluates its draft and finds that one claim has low confidence. It sends another request to the Researcher Agent:

The Researcher verifies the claim using fact-checking MCP servers and returns updated information:

Step 9: Reporter revises and submits to Editor

The Reporter incorporates the verified facts and sends the completed draft to the Editor Agent via A2A:

Step 10: Editor reviews using MCP tools

The Editor Agent uses multiple MCP servers to review the article:

The Editor approves the article and sends it forward:

Step 11: Publisher publishes via CI/CD

Finally, the Printer Agent publishes the approved article using the MCP servers for the CMS and CI/CD pipeline:

The Publisher confirms publication via A2A:

Here is the complete sequence of the A2A workflow in the accompanying repository using the same Agents described above.

#	From	To	Action	Protocol	Description
1	User	News Chief	Assign Story	HTTP POST	User submits story topic and angle
2	News Chief	Internal	Create Story	-	Creates story record with unique ID
3	News Chief	Reporter	Delegate Assignment	A2A	Sends story assignment via A2A protocol
4	Reporter	Internal	Accept Assignment	-	Stores assignment internally
5	Reporter	MCP Server	Generate Outline	MCP/HTTP	Creates article outline and research questions
6a	Reporter	Researcher	Request Research	A2A	Sends questions (parallel with 6b)
6b	Reporter	Archivist	Search Archive	A2A JSONRPC	Searches historical articles (parallel with 6a)
7	Researcher	MCP Server	Research Questions	MCP/HTTP	Uses Anthropic via MCP to answer questions
8	Researcher	Reporter	Return Research	A2A	Returns research answers
9	Archivist	Elasticsearch	Search Index	ES REST API	Queries news_archive index
10	Archivist	Reporter	Return Archive	A2A JSONRPC	Returns historical search results
11	Reporter	MCP Server	Generate Article	MCP/HTTP	Creates article with research/archive context
12	Reporter	Internal	Store Draft	-	Saves draft internally
13	Reporter	News Chief	Submit Draft	A2A	Submits completed draft
14	News Chief	Internal	Update Story	-	Stores draft, updates status to "draft_submitted"
15	News Chief	Editor	Review Draft	A2A	Auto-routes to Editor for review
16	Editor	MCP Server	Review Article	MCP/HTTP	Analyzes content using Anthropic via MCP
17	Editor	News Chief	Return Review	A2A	Sends editorial feedback and suggestions
18	News Chief	Internal	Store Review	-	Stores editor feedback
19	News Chief	Reporter	Apply Edits	A2A	Routes review feedback to Reporter
20	Reporter	MCP Server	Apply Edits	MCP/HTTP	Revises article based on feedback
21	Reporter	Internal	Update Draft	-	Updates draft with revisions
22	Reporter	News Chief	Return Revised	A2A	Returns revised article
23	News Chief	Internal	Update Story	-	Stores revised draft, status to "revised"
24	News Chief	Publisher	Publish Article	A2A	Auto-routes to Publisher
25	Publisher	MCP Server	Generate Tags	MCP/HTTP	Creates tags and categories
26	Publisher	Elasticsearch	Index Article	ES REST API	Indexes article to news_archive index
27	Publisher	Filesystem	Save Markdown	File I/O	Saves article as .md file in /articles
28	Publisher	News Chief	Confirm Publication	A2A	Returns success status
29	News Chief	Internal	Update Story	-	Updates story status to "published"

Conclusion

Both A2A and MCP have important roles to play in the modern augmented-LLM infrastructure paradigm. A2A offers flexibility for complex multi-agent systems but potentially less portability and higher operational complexity. MCP offers a standardized approach for tool integration that's simpler to implement and maintain, though it's not designed to handle multi-agent orchestration.

The choice isn't binary. As demonstrated through our newsroom example, the most sophisticated and effective LLM-backed systems often combine both approaches: agents coordinate and specialize through A2A protocols while accessing their tools and resources through MCP servers. This hybrid architecture provides the organizational benefits of multi-agent systems alongside the standardization and ecosystem advantages of MCP. This suggests that there may not need to be a choice at all: simply use both as a standard approach

It's up to you as a developer or architect to test and determine the best mixture of both solutions to create the right outcome for your specific use case. Understanding the strengths, limitations, and appropriate applications of each approach will enable you to build more effective, maintainable, and scalable AI systems.

Whether you're building a digital newsroom, a customer service platform, a research assistant, or any other LLM-powered application, carefully considering your coordination needs (A2A) and tool access requirements (MCP) will set you on the path to success.