API reference · CAIN Guard

Register A2A Card

POST /fabric/guard/a2a/register

Last reviewed 2026-11-06

POST /fabric/guard/a2a/register

Request body

A2ARegisterRequest (required)

Field	Type	Meaning
`agent_id` required	string
`capabilities` required	array of string	min items `1`
`endpoint_url`	string or null

Responses

Status	Meaning	Body
`200`	Successful Response	JSON
`401`	The X-API-Key header is missing, or the key is unknown, revoked or replaced.	`Error`
`403`	The key is valid but may not do this (for example an agent key approving its own held action).	`Error`
`422`	Validation Error	`HTTPValidationError`
`429`	Rate limit or monthly quota reached. Wait for the number of seconds in Retry-After when it is sent.	`Error`

Try it

Your API key X-API-Key Remember the key in this tab onlyRequest body application/json

This call changes data in the account the key belongs to.

The request goes from your browser straight to this site. Your key is not stored unless you tick the box, and then only in this tab's session storage.

Code

curl -sS -X POST 'https://cainstudio.online/fabric/guard/a2a/register' \
  -H "X-API-Key: $CAIN_API_KEY" \
  -H 'Content-Type: application/json' \
  -d '{"agent_id": "agent-id", "capabilities": ["capabilities"]}'

import json, os, urllib.request

req = urllib.request.Request('https://cainstudio.online/fabric/guard/a2a/register', method='POST',
    headers={"X-API-Key": os.environ["CAIN_API_KEY"], "Content-Type": "application/json"},
    data=json.dumps({
      "agent_id": "agent-id",
      "capabilities": [
        "capabilities"
      ]
    }).encode())
with urllib.request.urlopen(req, timeout=60) as r:
    print(r.status, json.load(r))

const res = await fetch("https://cainstudio.online/fabric/guard/a2a/register", {
  method: "POST",
  headers: {
    "X-API-Key": process.env.CAIN_API_KEY!,
    "Content-Type": "application/json",
  },
  body: JSON.stringify({
    "agent_id": "agent-id",
    "capabilities": [
      "capabilities"
    ]
  }),
});
console.log(res.status, await res.json());

Schemas used

A2ARegisterRequest · Error · HTTPValidationError · ValidationError

← Observe Capability · all 10 CAIN Guard calls · Revoke Card →

Try CAIN-42 on your own agents

Create a free account and every new account starts with a 30-day trial of the full platform. Or try the sandbox first, with no account at all.

Create a free account → · Try the sandbox · See the whole ecosystem