# A2A agents

> Goal: put the traffic between agents (A2A v1.0) through the gateway - under a quota, an audit and a verified identity - without the gateway terminating the…

Guide - Since version 1.2.0 - Flexway v1.6.3 - https://flexway.io/en/docs/operations-a2a/

> Operations guide: configure, deploy and observe the gateway. What the capability does, product side: [product guide](https://flexway.io/en/docs/product-overview/); calling it: [developer guide](https://flexway.io/en/docs/developer-overview/).

**Goal**: put the traffic **between** agents (A2A v1.0) through the gateway - under a quota, an audit
and a verified identity - without the gateway terminating the protocol. *Available since `1.2.0`; verifying upstream cards, the re-signed published card, agent-to-agent delegation and the
registry are planned for `1.9.0`.*

**What the gateway does, and does not.** It routes, authenticates, holds the `tenant`, counts, guards
push targets, relays without buffering and audits without content. It keeps **no** task and delivers
**no** webhook: the upstream agent binds each task to the identity it receives - a **requirement** for
the agent's team (another caller must get "task not found").

**Declare an agent.** Its v1.0 agent card is a **contract** versioned in Git, listed in
`contracts.a2a`; its `supportedInterfaces` carry the **gateway's** addresses (JSONRPC, HTTP+JSON - gRPC
refused); `x-flexway-a2a` says what is Flexway's and is not published. The upstream is `protocol: a2a`
and declares `token_exchange` - refused at load otherwise. Each security scheme of the card must match
a configured mechanism (`openIdConnectSecurityScheme` -> the discovery of an issuer of
`auth.issuers`). Until upstream card verification ships (planned for `1.9.0`), `verify: none` is **required**: the upstream's card is not verified, and
the diff says so. Full example: [A2A agent behind the gateway](https://flexway.io/en/docs/operations-examples-a2a/).

**Quotas and streams.** Writing costs (`write`), reading a task is free (`free`: no bucket, no tenant
quota); `x-flexway-a2a.methods` changes a method's class. `SendStreamingMessage` and `SubscribeToTask`
take a place of `max_streams` (per caller and per replica) and last at most `max_task_duration` -
past it, the stream **ends**; a longer task is followed with `GetTask`.

**Push notifications.** Closed by default: without `agents.a2a.push.allowed_hosts`, none. With it:
`https` only, a listed name (or under a `*.domain`), never an address in any form. The gateway does not
resolve the name: a permitted name later pointing inside is for the delivering agent to watch.

**The published card.** `GET <path of the first interface>/.well-known/agent-card.json`: the declared
card without `x-flexway-a2a`, anonymous, with an `ETag`. Give this URL to calling agents. Unsigned
until `1.9.0`. The extended card is relayed, at the gateway's addresses, never cached.

**Check.**

- the published card answers, without `x-flexway-a2a`;
- a JSON-RPC `SendMessage` then an HTTP+JSON `GetTask` answer, with `A2A-Version: 1.0`;
- the upstream agent receives a token of **its** audience, never the caller's;
- `/config` (admin) shows `a2a.agents`: bindings, methods and classes;
- `flexway_a2a_calls_total` counts by agent, method, binding and outcome.