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A2A Protocol & A2A Servers Flashcards

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1
Q

What does A2A stand for?

A

Agent-to-Agent

It is an open, application-layer protocol for AI agents to discover, exchange messages, and collaborate. A2A was announced publicly on April 9, 2025 (at Google Cloud Next)

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2
Q

When was A2A introduced publicly?

A

A2A was announced publicly on April 9, 2025 (at Google Cloud Next)April 2025

A2A is designed to complement tool-calling protocols like MCP.

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3
Q

What is the primary purpose of A2A?

A
  • Interoperability
  • Secure information exchange
  • Multi-agent workflows

A2A allows agents from different vendors to communicate and coordinate effectively.

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4
Q

What is the typical protocol shape of A2A?

A

JSON-RPC 2.0 over HTTP(S)

It supports streaming and push events for real-time updates.

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5
Q

What does a Green flag indicate in beach safety?

A

Safe, open conditions for swimming

Beach flags communicate water safety conditions.

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6
Q

What does a Red flag signify?

A

Unsafe conditions, closed for swimming

This is part of the universal system for water safety.

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7
Q

What is the difference between A2A and MCP?

A
  • MCP connects an agent to tools/data
  • A2A connects agents to each other

They are complementary protocols often used together.

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8
Q

What is the significance of multi-agent workflows?

A

They enable collaboration between different bots (e.g., procurement bot ↔️ travel bot ↔️ finance bot)

This reduces dependency on a single vendor.

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9
Q

True or false: A2A is intended to replace tool-calling protocols like MCP.

A

FALSE

A2A is meant to complement, not replace, existing protocols.

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10
Q

What does security posture refer to in the context of A2A?

A

Securely exchange information and act across enterprise apps

Authentication and authorization details depend on implementation.

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11
Q

What does A2A enable in terms of agent interactions?

A

An agent sends a JSON-RPC request describing an intent

The peer agent replies or streams progress/events.

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12
Q

What does the term agentic internet refer to?

A

Emerging infrastructure for AI agents alongside protocols like MCP and AP2

It represents a new era of agent interoperability.

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13
Q

What is a potential confusion regarding the term A2A?

A

It is also used for decentralized-identity (SSI) agent-to-agent messaging

This refers to a different ecosystem focused on verifiable credentials.

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14
Q

What is an A2A server?

A

A network service that implements the Agent-to-Agent (A2A) protocol

It serves as the public-facing agent endpoint that advertises the agent’s capabilities and interacts with peer agents.

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15
Q

List the main functions of an A2A server.

A
  • Expose agent capabilities as callable methods
  • Handle discovery & metadata
  • Process synchronous or async jobs
  • Enforce authn/authz & identity

These functions enable effective communication and collaboration between agents.

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16
Q

What does an A2A server expose as callable methods?

A
  • agent.describe
  • agent.execute

These methods allow other agents to interact with the A2A server’s capabilities.

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17
Q

What is the purpose of discovery & metadata in an A2A server?

A

To allow peers to find the agent and understand inputs/outputs

This is often facilitated via a manifest/schema.

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18
Q

What type of jobs can an A2A server process?

A
  • Synchronous jobs
  • Asynchronous jobs

It returns structured results or errors using A2A message formats.

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19
Q

What is the difference between an A2A server and an MCP server?

A
  • A2A server: agent↔agent collaboration
  • MCP server: agent↔tool/data access

They are complementary and often used together.

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20
Q

What is an example of a vendor runtime that allows creating A2A servers?

A

Amazon Bedrock AgentCore

It enables the creation and deployment of A2A servers and invocation from other agents.

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21
Q

What is the minimal request shape for an A2A server?

A

{
“jsonrpc”: “2.0”,
“id”: “42”,
“method”: “agent.execute”,
“params”: { “task”: “check_inventory”, “sku”: “ABC-123” }
}

This request shape illustrates how an A2A server validates and executes tasks.

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22
Q

True or false: An A2A server can stream updates.

A

TRUE

It can execute tasks and possibly stream updates as part of its functionality.

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23
Q

What is the purpose/scope of an A2A server?

A

Exposes an agent to other agents for interop (delegate tasks, negotiate, stream status)

A2A servers facilitate communication and collaboration between different agents.

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24
Q

Who typically communicates with an A2A server?

A

Other agents (often from other vendors/runtimes)

A2A servers are designed for interoperability among various agents.

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25
What is the **message model** used by an **A2A server**?
JSON-RPC 2.0 methods (e.g., `agent.describe`, `agent.execute`) + streaming events ## Footnote This model allows for structured communication and event handling.
26
What transport protocols are typically used by an **A2A server**?
Typically HTTPS; many stacks add Server-Sent Events (SSE) for progress ## Footnote This ensures secure and real-time communication.
27
What is the **discovery/metadata** mechanism for an **A2A server**?
“Agent Card” (JSON) advertises identity, skills, auth, endpoint ## Footnote The Agent Card provides essential information for other agents to interact with it.
28
What are the **authentication/authorization** methods for an **A2A server**?
Implementation-defined (tokens/TLS; some runtimes add policy layers) ## Footnote Security measures can vary based on the specific implementation.
29
What is the **state model** of an **A2A server**?
Often task/session-oriented with progress streaming ## Footnote This allows for tracking the state of ongoing tasks and interactions.
30
What is a **typical use** case for an **A2A server**?
Multi-agent workflows (e.g., procurement agent ↔ finance agent) ## Footnote A2A servers are commonly used in scenarios requiring collaboration between different agents.
31
Name an **example** of an **A2A server**.
Google’s A2A announcement/spec; A2A in Bedrock AgentCore; LangSmith A2A endpoints ## Footnote These examples illustrate the practical application of A2A servers.
32
What is the **OSI layer** placement of **A2A and MCP**?
**Application-layer protocols that usually run *over* HTTP/SSE** and define domain-specific *message contracts* above HTTP ## Footnote This means they rely on HTTP for transport while providing specialized functionality.
33
What does **HTTP** represent in the OSI model?
The road for request/response lanes, headers, status codes ## Footnote HTTP is a layer 7 protocol running atop layers 4, 3, 2, and 1.
34
What does **MCP** add on top of HTTP?
* Standardized power adaptor for tools * Defines how to talk to tools and data sources * Uses JSON-RPC for messages and roles ## Footnote MCP rides on top of HTTP (or STDIO) and provides uniform tool schemas.
35
What does **A2A** facilitate between agents?
* Standardized handshake between agents * Describes skills, delegates tasks, streams progress ## Footnote A2A typically rides on top of HTTP/SSE using JSON-RPC.
36
What are the **three main concerns** addressed by HTTP, MCP, and A2A?
* Endpoint meaning * Message schema * Conversation shape ## Footnote Each layer adds specific functionalities to enhance communication.
37
In the context of HTTP, what does **endpoint meaning** refer to?
A URL that accepts messages ## Footnote This is the basic definition of how HTTP endpoints function.
38
What does MCP add to the **message schema** in comparison to HTTP?
JSON-RPC methods for capability listing, prompts, tool calls ## Footnote MCP enhances the message schema by defining specific interactions.
39
What is the **conversation shape** characteristic of HTTP?
Stateless by default; app-defined ## Footnote This means that each request is independent and does not retain state.
40
What does A2A define regarding **conversation shape**?
Task/session lifecycle; progress streaming/notifications ## Footnote A2A enhances the interaction by maintaining context and progress.
41
What transport protocols can be used with HTTP?
* TCP (HTTP/1.1, HTTP/2) * QUIC (HTTP/3) ## Footnote These protocols ensure flow control and reliability.
42
What is the role of **JSON** in A2A and MCP?
Serialization of messages over HTTP/SSE or STDIO ## Footnote JSON is commonly used for data interchange in these protocols.
43
What does the **MCP** protocol define regarding tools?
How to call tools/resources in a uniform way ## Footnote This standardization helps in interoperability between different systems.
44
What is the significance of **separation of concerns** in design?
Keeps transport changes independent from application contracts ## Footnote This allows for easier updates and maintenance of systems.
45
What does **observability & security** refer to in the context of HTTP?
* HTTP-layer controls (TLS, OAuth, mTLS) * Mesh policies at L7 ## Footnote These controls help manage security and monitoring at the transport layer.
46
What does **resilience** mean in the context of HTTP and A2A/MCP?
* Retries, backoff, idempotency at HTTP/transport * Task compensation and DAG orchestration in A2A/MCP ## Footnote This ensures that systems can recover from failures effectively.
47
What is the **OSI placement** of HTTP?
Application layer (RFC semantics) over TCP/QUIC ## Footnote This defines where HTTP fits within the OSI model.
48
What is the **OSI placement** of MCP and A2A?
Application-layer protocols, domain-specific on top of HTTP ## Footnote They define meaningful contracts that enhance communication between agents.
49
What is the **minimal viable reference architecture** for a network of agents?
* Ingress (HTTP): API gateway / load balancer terminating TLS; SSE enabled for streams * Agent endpoints (A2A servers): Each domain agent exposes an A2A JSON-RPC endpoint and an **Agent Card** for discovery * Tool adapters (MCP servers): Uniform connectors for files, repos, calendars, browsers, DBs * Orchestrator (host): Your “supervisor” assistant that calls tools via MCP and delegates subtasks to peer agents via A2A ## Footnote This architecture outlines the foundational components necessary for agent interoperability.
50
What does a **Green flag** indicate in beach flag safety?
Safe, open conditions for swimming ## Footnote Beach flags are a universal system to communicate water safety conditions.
51
What does a **Yellow flag** mean in beach flag safety?
Caution, limited swimming ## Footnote Beach flags are a universal system to communicate water safety conditions.
52
What does a **Red flag** signify in beach flag safety?
Unsafe conditions, closed for swimming ## Footnote Beach flags are a universal system to communicate water safety conditions.
53
What does a **Purple flag** warn about in beach flag safety?
Dangerous marine life ## Footnote Beach flags are a universal system to communicate water safety conditions.
54
Fill in the blank: The **host** pulls context through **MCP** and composes requirements when a user asks to __________.
Book Chicago trip ## Footnote This is part of the flow in the happy path for agent interaction.
55
What is the role of the **Orchestrator** in the agent network?
Calls tools via MCP and delegates subtasks to peer agents via A2A ## Footnote The orchestrator acts as a supervisor assistant.
56
What is the purpose of **mTLS/OAuth** at the gateway?
Identity, auth, policy ## Footnote This is part of the production hardening checklist.
57
What should be used for **transport & delivery** in the network of agents?
HTTP/2 or HTTP/3 with keep-alive; expose a **/events** SSE stream for progress ## Footnote This is part of the production hardening checklist.
58
True or false: **Idempotent `agent.execute`** is recommended for client-supplied `id`.
TRUE ## Footnote This is part of the reliability guidelines in the production hardening checklist.
59
What are the suggested **component picks** for A2A servers?
* LangSmith Agent Server * Bedrock **AgentCore Runtime** ## Footnote These components are recommended for building A2A servers.
60
What is the **first step** in the team-ready blueprint for building the agent network?
Stand up one MCP host + two MCP servers (Files, Git) and prove tool calls from the host ## Footnote This is the initial step in the development process.
61
What is the purpose of **Agent Cards** in the A2A architecture?
Discovery of agents and their capabilities ## Footnote Agent Cards are essential for agent interoperability.
62
Fill in the blank: **Version your Agent Card** and MCP tool schemas; use canary agents behind distinct A2A routes (e.g., __________).
/a2a/v2/... ## Footnote This is part of the versioning & contracts guidelines.
63
What is a key design heuristic regarding **roles** in the agent network?
Keep roles clean: *A2A = delegate to peers; MCP = use tools* ## Footnote This helps maintain clarity in the architecture.
64
What does **observability** entail in the context of the agent network?
Centralize traces/spans for `agent.execute` and MCP tool calls; record inputs/outputs with PII controls ## Footnote Observability is crucial for monitoring and debugging.
65
What does **A2A** stand for in the context of application layer protocols?
Agent-to-Agent ## Footnote A2A standardizes how agents communicate with each other. A2A was announced publicly on April 9, 2025 (at Google Cloud Next)
66
What is the primary function of **MCP**?
Standardizes how an AI host talks to tools and data sources ## Footnote MCP defines capabilities, tool calls, and resource access for uniform invocation of adapters.
67
What does **HTTP** define in its protocol?
* Request/response semantics * Headers * Status codes * Transports (HTTP/1.1, /2, /3 over TCP/QUIC) ## Footnote HTTP is a general-purpose web protocol that operates at the application layer.
68
Fill in the blank: **MCP** sits ______ **HTTP** and standardizes communication between an AI host and tools.
above ## Footnote MCP defines how hosts can invoke tools uniformly.
69
What are the key differences between **HTTP**, **MCP**, and **A2A** in terms of scope?
* HTTP = transport & generic web semantics * MCP = host↔tool contract * A2A = agent↔agent contract ## Footnote Each protocol serves a different purpose within the application layer.
70
True or false: **MCP** and **A2A** both specify message schemas, roles, and lifecycles that can be carried over **HTTP**.
TRUE ## Footnote They commonly use streaming methods like SSE.
71
What role does **HTTP** play in the modern stack?
Delivery ## Footnote HTTP is typically used for transporting messages in the application layer.
72
What does **A2A** define regarding agent communication?
* Discovery/identity * Task delegation * Sessions * Progress/events ## Footnote A2A standardizes interactions between peer agents.
73
In terms of roles, how does **MCP** differ from **A2A**?
* MCP = host–server * A2A = peer agents ## Footnote This distinction highlights their different functions in communication.
74
What type of metadata does **MCP** advertise?
Tools/resources ## Footnote MCP provides information necessary for the host to access various tools.
75
What is the relationship between **MCP**, **A2A**, and **HTTP** in a modern stack?
Complementary layers, not competitors ## Footnote Each protocol serves a unique purpose while working together.
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