curl -X GET "$KONNECT_PROXY_URL/a2a/.well-known/agent-card.json" \
--no-progress-meter --fail-with-body \
-H "apikey: a2a-secret-key-1"
Rate limit A2A traffic
Enable the Rate Limiting Advanced plugin on the same service or route as the AI A2A Proxy plugin. Combined with an authentication plugin, rate limits apply per consumer. Requests that exceed the limit are rejected with 429.
Prerequisites
Kong Konnect
This is a Konnect tutorial and requires a Konnect personal access token.
-
Create a new personal access token by opening the Konnect PAT page and selecting Generate Token.
-
Export your token to an environment variable:
export KONNECT_TOKEN='YOUR_KONNECT_PAT'Copied! -
Run the quickstart script to automatically provision a Control Plane and Data Plane, and configure your environment:
curl -Ls https://get.konghq.com/quickstart | bash -s -- -k $KONNECT_TOKEN --deck-outputCopied!This sets up a Konnect Control Plane named
quickstart, provisions a local Data Plane, and prints out the following environment variable exports:export DECK_KONNECT_TOKEN=$KONNECT_TOKEN export DECK_KONNECT_CONTROL_PLANE_NAME=quickstart export KONNECT_CONTROL_PLANE_URL=https://us.api.konghq.com export KONNECT_PROXY_URL='http://localhost:8000'Copied!Copy and paste these into your terminal to configure your session.
Kong Gateway running
This tutorial requires Kong Gateway Enterprise. If you don’t have Kong Gateway set up yet, you can use the quickstart script with an enterprise license to get an instance of Kong Gateway running almost instantly.
-
Export your license to an environment variable:
export KONG_LICENSE_DATA='LICENSE-CONTENTS-GO-HERE'Copied! -
Run the quickstart script:
curl -Ls https://get.konghq.com/quickstart | bash -s -- -e KONG_LICENSE_DATACopied!Once Kong Gateway is ready, you will see the following message:
Kong Gateway Ready
decK v1.43+
decK is a CLI tool for managing Kong Gateway declaratively with state files. To complete this tutorial, install decK version 1.43 or later.
This guide uses deck gateway apply, which directly applies entity configuration to your Gateway instance.
We recommend upgrading your decK installation to take advantage of this tool.
You can check your current decK version with deck version.
Required entities
For this tutorial, you’ll need Kong Gateway entities, like Gateway Services and Routes, pre-configured. These entities are essential for Kong Gateway to function but installing them isn’t the focus of this guide. Follow these steps to pre-configure them:
-
Run the following command:
echo ' _format_version: "3.0" services: - name: a2a-currency-agent url: http://host.docker.internal:10000 routes: - name: a2a-route paths: - "/a2a" strip_path: true service: name: a2a-currency-agent protocols: - http - https ' | deck gateway apply -Copied!
To learn more about entities, you can read our entities documentation.
OpenAI API key
This tutorial uses OpenAI:
- Create an OpenAI account.
- Get an API key.
-
Create a decK variable with the API key:
export DECK_OPENAI_API_KEY='YOUR OPENAI API KEY'Copied!
A2A agent
You need a running A2A-compliant agent. This guide uses a sample currency conversion agent from the A2A project.
Create a docker-compose.yaml file:
cat <<'EOF' > docker-compose.yaml
services:
a2a-agent:
container_name: a2a-currency-agent
build:
context: .
dockerfile_inline: |
FROM python:3.12-slim
WORKDIR /app
RUN pip install uv && apt-get update && apt-get install -y git
RUN git clone --depth 1 https://github.com/a2aproject/a2a-samples.git /tmp/a2a && \
cp -r /tmp/a2a/samples/python/agents/langgraph/* . && \
rm -rf /tmp/a2a
ENV UV_COMPILE_BYTECODE=1 UV_LINK_MODE=copy
RUN uv sync --frozen --no-dev
EXPOSE 10000
CMD ["uv", "run", "app", "--host", "0.0.0.0"]
environment:
- model_source=openai
- API_KEY=${DECK_OPENAI_API_KEY}
- TOOL_LLM_URL=https://api.openai.com/v1
- TOOL_LLM_NAME=gpt-5.1
ports:
- "10000:10000"
EOF
Export your OpenAI API key and start the agent:
export DECK_OPENAI_API_KEY='your-openai-key'
docker compose up --build -d
The agent listens on port 10000 and uses the A2A JSON-RPC protocol to handle currency conversion queries. In this guide, the gateway service points to host.docker.internal:10000 instead of the container name because Kong Gateway runs in its own container with a separate DNS resolver.
Enable the AI A2A Proxy plugin
The AI A2A Proxy plugin parses A2A JSON-RPC requests and proxies them to the upstream agent.
echo '
_format_version: "3.0"
plugins:
- name: ai-a2a-proxy
config:
logging:
log_statistics: true
log_payloads: true
' | deck gateway apply -
Enable the Key Auth plugin
The Key Auth plugin identifies callers and associates them with a Kong consumer. Rate Limiting Advanced uses this consumer identity to apply per-consumer limits.
echo '
_format_version: "3.0"
plugins:
- name: key-auth
' | deck gateway apply -
Enable the Rate Limiting Advanced plugin
The Rate Limiting Advanced plugin counts requests per consumer and rejects requests that exceed the configured limit. This configuration allows 5 requests per 30 seconds, intentionally low to make it easy to trigger during testing.
echo '
_format_version: "3.0"
plugins:
- name: rate-limiting-advanced
config:
limit:
- 5
window_size:
- 30
sync_rate: -1
namespace: a2a-currency-agent
strategy: local
' | deck gateway apply -
Set
limitandwindow_sizeto values appropriate for your production workload. The values in this guide are intentionally low for testing.
Validate rate limit headers
Send an authenticated request to the agent card endpoint and inspect the response headers. The agent card is a lightweight A2A operation (GetAgentCard) that returns agent metadata without calling an LLM, so responses are instant.
curl -X GET "http://localhost:8000/a2a/.well-known/agent-card.json" \
--no-progress-meter --fail-with-body \
-H "apikey: a2a-secret-key-1"
The response includes rate limit headers:
HTTP/2 200
...
ratelimit-limit: 5
ratelimit-remaining: 4
ratelimit-reset: 30
x-ratelimit-limit-30: 5
x-ratelimit-remaining-30: 4
ratelimit-remaining decreases with each request. ratelimit-reset shows the seconds until the window resets.
Validate rate limit enforcement
Send 6 requests to the agent card endpoint in a loop to exceed the limit. The AI A2A Proxy plugin detects each request as an A2A GetAgentCard operation, so the rate limit applies the same way it does for message/send or any other A2A method.
for i in $(seq 1 6); do
echo "--- Request $i ---"
curl -s -o /dev/null -w "HTTP status: %{http_code}\n"\
http://localhost:8000/a2a/.well-known/agent-card.json \
-H "apikey: a2a-secret-key-1"
done
for i in $(seq 1 6); do
echo "--- Request $i ---"
curl -s -o /dev/null -w "HTTP status: %{http_code}\n"\
$KONNECT_PROXY_URL/a2a/.well-known/agent-card.json \
-H "apikey: a2a-secret-key-1"
done
The first 5 requests return HTTP status: 200. The 6th request returns HTTP status: 429:
--- Request 1 ---
HTTP status: 200
--- Request 2 ---
HTTP status: 200
--- Request 3 ---
HTTP status: 200
--- Request 4 ---
HTTP status: 200
--- Request 5 ---
HTTP status: 200
--- Request 6 ---
HTTP status: 429
The 429 response body contains:
{
"message": "API rate limit exceeded"
}
Cleanup
Clean up Konnect environment
If you created a new control plane and want to conserve your free trial credits or avoid unnecessary charges, delete the new control plane used in this tutorial.
Destroy the Kong Gateway container
curl -Ls https://get.konghq.com/quickstart | bash -s -- -d
FAQs
Can I rate limit A2A traffic without authentication?
Yes. Without an authentication plugin, the Rate Limiting Advanced plugin falls back to rate limiting by IP address. Add an authentication plugin if you need per-consumer limits.
Does rate limiting affect A2A streaming responses?
Rate limiting applies at request time, before the upstream responds. A streaming SSE response that is already in progress is not interrupted. The rate limit check happens when the client sends the next request.
Can I use AI Rate Limiting Advanced instead?
AI Rate Limiting Advanced limits based on LLM token consumption (prompt and completion tokens). The AI A2A Proxy plugin does not extract token counts from A2A responses, so AI Rate Limiting Advanced has no token data to act on. Use the standard Rate Limiting Advanced plugin for A2A traffic.