Anuj Sadani / Field Guide

Contracts & knowledge · Specification

AsyncAPI

Describe message-driven interfaces through channels, operations, messages, and protocol details.

Intermediate · 3 drills · Reviewed 2026-10-24

See an examplePractise

What it helps you do

Make messaging interactions explicit where an HTTP request-response description is not enough.

Starting knowledge: Understand producers, consumers, and message channels.

  • Identify the application perspective and operation direction.
  • Describe channels, message payloads, and relevant protocol bindings.
  • State delivery and processing assumptions separately when they matter.

The problem it came from

The AsyncAPI Initiative develops a specification for describing asynchronous and event-driven interfaces. Its document model gives teams a shared description of messaging contracts.

The linked conceptual documentation explains the roles of channels, operations, and messages. Version-specific syntax should be checked against the edition a tool supports.

Work through an example

STARTING POINT
The workshop service tells notifications when someone registers.
APPLYING THE APPROACH
Application: workshop registration service
Operation: send registration-confirmed
Channel: workshop.registrations
Message: registration ID, workshop ID, participant contact reference
Consumer expectation: repeated message IDs must not send duplicate confirmations
This is a conceptual contract sketch, not versioned AsyncAPI YAML.
  • Direction is defined from the named application’s perspective.
  • The message has an identity useful for duplicate handling.
  • The processing requirement still needs implementation evidence.

Where it helps. Where it stops.

Use it when

  • Services exchange events or commands through a broker.
  • Teams need to agree message names, payloads, and producer/consumer responsibilities.

Potential benefits

  • A shared message contract can expose ambiguous ownership.
  • Payload and channel descriptions support documentation and compatible tooling.

Limits and common mistakes

  • A contract does not guarantee delivery, ordering, or exactly-once processing.
  • Describing a message does not make every consumer safe under retries or duplicates.
Applying it with AI

The prompt below asks for this structure. It does not guarantee accuracy, complete coverage, better learning, or conformance to a standard. Treat those outcomes as separate checks.

Practise the judgment

Try a choice, inspect a boundary, then explain a case yourself. Hints and answers are available whenever you need them.

DRILL 01 Not attempted

Why state the application perspective?

Choose one answer
Hint

Direction is relative to the application.

Explained answer

Best answer for this case: Because send and receive depend on which application is described

The same message may be sent by one application and received by another.

Link to this drill
DRILL 02 Not attempted

Does a message contract prove that duplicate delivery has no duplicate effect?

Choose one answer
Hint

A valid event can be delivered twice.

Explained answer

Best answer for this case: No; the consumer’s processing must be checked

Duplicate-safe processing is behavior beyond describing the message shape.

Link to this drill
DRILL 03 Not attempted

What would you add to a notification contract to discuss duplicate delivery?

Hint

What ties two deliveries to one logical event?

Explained answer & self-review rubric

Give messages a stable identity, state the retry/delivery assumptions, and specify whether the consumer deduplicates effects. Add a repeated-delivery scenario and check the implementation.

  • Identify messages
  • State processing expectations
  • Retain an executable or reviewable repeat case
Link to this drill

Take it into your own work

Manual template

Use this structure yourself, with a colleague, or in your preferred writing tool.

# Message interface
AsyncAPI edition:
Application and operation direction:
Channel:
Message name and identity:
Payload schema:
Protocol binding:
Ordering, retry, and duplicate assumptions:
Consumer behavior:
Compatibility policy:
Download template (.md)

Review the result

  • Whose send/receive perspective is used?
  • Are message identities and payloads explicit?
  • Are delivery guarantees distinguished from assumptions?
Use this approach with your own AI tool
Help me apply AsyncAPI to the material below.
Reader and existing knowledge: [describe]
Task and desired outcome: [describe]
Use these principles: Identify the application perspective and operation direction.; Describe channels, message payloads, and relevant protocol bindings.; State delivery and processing assumptions separately when they matter..
Preserve source facts, identifiers, quantities, conditions, exceptions, and uncertainty.
Separate supplied facts from assumptions. Ask for missing information instead of inventing it.
Explain your representation choices and provide a review checklist. Do not claim formal compliance or correctness from formatting alone.
Material: [paste only information you are permitted to share]
Download prompt

Go to the source

History and the underlying approach are grounded in these references. Examples, prompts, and practice cases here are original educational adaptations. Edition-specific details should be checked against the referenced publication.

Last editorial review: 2026-10-24. An overview is not certification, and this guide is not a reproduction of a standard.