A2A Protocol v0.3.0 Validator

Quick Check: Is Your Agent Card Valid?

Before you publish, before you deploy, let's make sure the basics work.

This web validator checks A2A protocol compliance—catching JSON errors and schema problems. It's your first sanity check, not your last.

Agent Card Input
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Ready to Validate

Enter your agent card JSON or URL and click validate to get started

What You Just Tested (And What You Didn't)

This Web Validator Checks
✓
JSON syntax - Does it parse without errors?
✓
Required fields - Is name, version, capabilities present?
✓
Basic structure - Does it look like an agent card?

Perfect for: Catching typos and malformed JSON before you commit.

This Web Validator Can't Check
✗
Live endpoints - Are your URLs actually reachable?
✗
Signatures - Is this agent who it claims to be?
✗
Protocol compliance - Does it respond to A2A messages correctly?

Why: Browsers can't make arbitrary network requests or verify cryptographic signatures.

When to Use Which Tool

Different stages of development need different validation. Here's when each tool makes sense.

🎨

You're writing your first agent card

Use this web validator to catch syntax errors as you type. Quick feedback loop, no installation hassle.

Pro tip: Keep this page open in a tab while you edit your JSON. Paste, check, fix, repeat.
🚀

You're about to deploy to production

Now you need the CLI tool. It actually connects to your endpoints, verifies your signatures, and confirms your agent responds correctly.

Security note: The CLI validates cryptographic signatures. This web tool can't do that—browsers don't have access to system crypto libraries.
🔍

You're evaluating a third-party agent

Start here for a quick sanity check. Then use the CLI to verify the signature actually matches the claimed identity and test if their endpoints are really available.

Trust matters: Anyone can write a valid JSON file. Signature verification proves the agent is who they claim to be.
⚙️

You're setting up automated testing

The CLI only. It outputs JSON and SARIF formats for CI/CD integration, runs headless, and provides proper exit codes for pipeline automation.

Example: capiscio validate ./agent.json --json --errors-only

The Schema-Reality Gap

Here's what actually fails in production (and what this web tool can't catch):

  • →
    Your endpoint URL is correct in JSON, but it's not reachable
    Firewall rules, DNS issues, SSL certificate problems—the web validator never tries to connect.
  • →
    Your signature looks valid, but it's signed by the wrong key
    Or expired. Or the JWKS URL is unreachable. The web tool can't verify cryptographic signatures.
  • →
    Your agent card claims JSONRPC support, but returns malformed responses
    Protocol compliance requires actually testing the transport layer. Browsers can't do that.
  • →
    Everything validates, but your agent times out under load
    Availability scoring requires live endpoint testing with realistic traffic patterns.

This is why the CLI exists. Schema validation is step one. Testing reality is step two.

Get the CLI Tool

Ready for Production Validation?

Three steps. Five minutes. Full validation.

1

Install the CLI

npm install -g capiscio-cli

Or use Python (pip install capiscio) or download a standalone binary—no dependencies required.

2

Run validation with all checks

capiscio validate ./agent-card.json

This tests schema, endpoints, signatures, and protocol compliance. You'll get a three-dimensional score: Compliance, Trust, and Availability.

3

Fix what fails, then deploy

The CLI tells you exactly what's wrong: unreachable endpoints, invalid signatures, protocol violations. Fix those, re-run validation, and you're ready to ship.

Bonus: Add it to your CI/CD pipeline with --json --errors-only for automated testing.

Additional Installation Options

Choose your installation method:
Node.js:
npm install -g capiscio-cli
Python:
pip install capiscio
Standalone Binary (No Dependencies):
Validate with signature verification (automatic):
capiscio validate ./agent-card.json
Test actual endpoints:
capiscio validate https://agent.com
CI/CD integration:
capiscio validate ./agent.json --json --errors-only

Ready to Validate Like a Pro?

You've seen the basics work. The CLI unlocks the full power: live endpoint testing, cryptographic signatures, and CI/CD automation.

Web ✓
Schema Validation
What you just used
CLI +
Live Endpoints
Actually test your agent
CLI +
JWS Signatures
Cryptographic proof

Stop guessing if your agent works. Test it for real.

Stop Testing Schemas. Start Testing Reality.

Move beyond basic validation. Test live endpoints, verify signatures, automate your pipeline.

CLI Documentation →