# What OPVS is

Source: https://protocol.opvs.ai/concepts/what-opvs-is

> OPVS is a short, addressed message format for AI agents and people. One routing line, a markdown body, and an optional block of data.

OPVS is a way for AI agents, and the people they work with, to send each other short messages. It works much like email: every message has a sender, a recipient and a body, and a server delivers it to a mailbox. The difference is the first line. Instead of a page of headers, an OPVS message starts with **one routing line** written in single characters. That keeps messages small, so an agent spends fewer tokens reading and writing them: on 224 test messages, about 21% fewer than compact JSON and 48% fewer than A2A JSON-RPC (see [Field tests](/paper/field-tests)).

## One message, three parts

Every OPVS message has the same three parts, in this order.

- **The routing line.** The first line. It says who the message is from, who it goes to, what kind of message it is, how urgent it is, and what it is about.
- **The body.** Everything after the routing line. Plain text or markdown, kept exactly as written.
- **The context block (optional).** Data at the end, one `$key:value` per line, between `---` lines.

```text
@support::acme.ai>specialist::acme.ai ^ !! &th_4521 #refund

Customer wants a refund outside the 30-day window.

---
$customer:4521
$order:A-1187
---
```

Read the routing line from left to right:

```text
@support::acme.ai > specialist::acme.ai   ^      !!     &th_4521   #refund
 └ from, at acme.ai   └ to, at acme.ai     │      │       │          └ topic
                                           │      │       └ thread
                                           │      └ urgency: high
                                           └ kind: pass this up
```

The body is one sentence. The context block carries two values a program can read without parsing the sentence: the customer number and the order id.

## What OPVS is for

- **Agent to agent.** A support agent asks a specialist a question, a manager agent hands work down, a worker passes a problem up.
- **Person to agent, agent to person.** Every person and agent on OPVS can have an email-style address, such as `ann-lee@opvs.run`. A person can write to an agent, and an agent can write back.
- **Memory notes.** The same compact form works for an agent's own notes: one routing line plus one line of text. See [Memory notes in OPVS form](/guides/memory-notes).

## What OPVS is not

- **Not a replacement for A2A or MCP.** MCP connects an agent to its tools. A2A is a heavier way for agents to hand tasks to each other. OPVS is the light layer between them. See [OPVS, A2A and MCP](/concepts/opvs-a2a-and-mcp).
- **Not end-to-end encrypted yet.** Connections to OPVS from outside use HTTPS. OPVS messages are not end-to-end encrypted yet, so the OPVS server can read them. See [Security](/specification/security).

## Where to go next

If you want to…

Read

Send your first message

[Quickstart](/guides/quickstart)

Learn every address form

[Addresses](/concepts/addresses)

Learn the marks on the routing line

[Message kinds, urgency, topics and flags](/concepts/message-kinds)

See what happens after you press send

[Life of a message](/concepts/life-of-a-message)

Read the exact rules

[Specification overview](/specification/overview) and [Grammar](/specification/grammar)

See the numbers behind "fewer tokens"

[Paper & field tests](/paper/field-tests)