CapiscIO CLI - A2A Protocol Validator

Comprehensive validation for AI agent trust and protocol compliance | Beyond schema validation - test cryptographic authenticity and live protocol functionality.

🌐 Learn more about CapiscIO | Download Page | Web Validator

Common A2A Integration Challenges

Agent cards can pass schema validation but fail in production due to real-world integration issues.

What Often Goes Wrong:

• 🔌 Endpoint connectivity - declared URLs return 404 or timeout
• ⚠️ Protocol implementation gaps - JSONRPC/GRPC errors in production
• 🔒 Missing cryptographic signatures - no way to verify agent authenticity
• 📋 Specification compliance - subtle A2A protocol violations
• ❌ Schema vs reality - valid JSON but broken functionality

How CapiscIO Helps:

• 🔒 JWS signature verification - cryptographically verify agent authenticity
• 🌐 Live endpoint testing - catch broken protocols before deployment
• ⚡ Zero-dependency validation - no npm vulnerabilities or Python conflicts
• 🛡️ Comprehensive validation - trust AND functionality in one command

Quick Start

💡 Prefer a web interface? Try our online validator at capisc.io - no installation required!

Option 1: Install via NPM (Requires Node.js)

# Install globally
npm install -g capiscio-cli

# Validate your agent
capiscio validate ./agent-card.json

# Test live endpoints
capiscio validate https://your-agent.com

# Strict validation for production
capiscio validate ./agent-card.json --strict --json

Option 2: Standalone Binary (Advanced)

If you don't want to use Node.js or Python, you can download the standalone Go binary directly from the capiscio-core repository. This is the engine that powers the CLI.

Download latest binaries from capiscio-core releases

| Platform | Architecture | Binary Name | |----------|-------------|-------------| | Linux | x64 | capiscio-linux-amd64 | | macOS | Intel | capiscio-darwin-amd64 | | macOS | Apple Silicon | capiscio-darwin-arm64 | | Windows | Intel x64 | capiscio-windows-amd64.exe |

Quick Download Example (Linux):

# Download the binary
curl -L -o capiscio https://github.com/capiscio/capiscio-core/releases/download/v1.0.2/capiscio-linux-amd64

# Make executable
chmod +x capiscio

# Run
./capiscio validate ./agent-card.json

Key Features

• 🔐 Two-Layer Validation - ONLY CapiscIO validates both cryptographic trust AND protocol compliance
• ✅ JWS Signature Verification - Cryptographic validation of agent authenticity (RFC 7515 compliant)
• 🚀 Live Protocol Testing - Actually tests JSONRPC, GRPC, and REST endpoints (not just schemas)
• ⚡ High Performance - Powered by a native Go binary for blazing fast validation
• 🛡️ Secure by Default - Signature verification enabled automatically
• 🔧 CI/CD Ready - JSON output with proper exit codes for automated pipelines
• 🌐 Smart Discovery - Finds agent cards automatically with multiple fallbacks
• 💻 Cross-Platform - npm or standalone binaries

Usage

Basic Commands

capiscio validate [input] [options]

# Examples
capiscio validate                              # Auto-detect in current directory
capiscio validate ./agent-card.json           # Validate local file (with signatures)
capiscio validate https://agent.com           # Test live agent (with signatures)
capiscio validate ./agent-card.json --skip-signature # Skip signature verification
capiscio validate ./agent-card.json --verbose # Detailed output
capiscio validate ./agent-card.json --registry-ready # Check registry readiness
capiscio validate https://agent.com --errors-only    # Show only problems
capiscio validate ./agent-card.json --show-version   # Version analysis

Key Options

| Option | Description | |--------|-------------| | --strict | Strict A2A protocol compliance | | --json | JSON output for CI/CD | | --verbose | Detailed validation steps | | --timeout | Request timeout (default: 10000) | | --schema-only | Skip live endpoint testing | | --skip-signature | Skip JWS signature verification | | --test-live | Test agent endpoint with real messages |

Live Agent Testing

The --test-live flag tests your agent endpoint with real A2A protocol messages:

# Test agent endpoint
capiscio validate https://agent.com --test-live

# Test with custom timeout
capiscio validate ./agent-card.json --test-live --timeout 5000

# Full validation for production
capiscio validate https://agent.com --test-live --strict --json

What it validates:

• ✅ Endpoint connectivity
• ✅ JSONRPC and HTTP+JSON transport protocols
• ✅ A2A message structure (Message, Task, StatusUpdate, ArtifactUpdate)
• ✅ Response timing metrics

Exit codes for automation:

• 0 = Success
• 1 = Schema validation failed
• 2 = Network error (timeout, connection refused, DNS)
• 3 = Protocol violation (invalid A2A response)

Use cases:

• CI/CD post-deployment verification
• Cron-based health monitoring
• Pre-production testing
• Third-party agent evaluation
• Multi-environment validation

Validation Modes

• Progressive (default): Balanced validation with warnings for compatibility issues
• Strict: Full compliance required, warnings become errors, registry-ready validation

Registry Ready: Use --registry-ready for strict validation optimized for agent registry deployment.

Three-Dimensional Scoring

CapiscIO CLI automatically provides detailed quality scoring across three independent dimensions:

# Scoring is shown by default
capiscio validate agent.json

Three Quality Dimensions:

• Spec Compliance (0-100) - How well does the agent conform to A2A v0.3.0?
• Trust (0-100) - How trustworthy and secure is this agent? (includes confidence multiplier)
• Availability (0-100) - Is the endpoint operational? (requires --test-live)

Each score includes a detailed breakdown showing exactly what contributed to the result.

Note: Legacy single-score output has been replaced by this multi-dimensional system in v2.0.0.

Why Use CapiscIO CLI?

Stop Integration Disasters Before They Happen:

🚨 What Breaks When You Don't Validate

• Compromised agents inject malicious responses - unsigned cards can't be trusted
• JSONRPC methods return wrong error codes - protocol violations cause failures
• GRPC services are unreachable or misconfigured - integration breaks silently
• REST endpoints don't match declared capabilities - runtime mismatches
• Tampered agent cards - man-in-the-middle attacks succeed
• Production failures cascade - one bad agent brings down your system

✅ CapiscIO Prevents These Failures

• JWS signature verification - cryptographically prove agent authenticity
• Live endpoint connectivity testing - catch broken protocols before deployment
• A2A protocol compliance validation - prevent specification violations
• HTTPS-only JWKS security - tamper-proof key distribution
• Real connectivity validation - beyond schema to actual functionality

The only CLI that validates both cryptographic trust AND protocol compliance.

Transport Protocol Testing & Security

Unlike basic schema validators, CapiscIO CLI actually tests your agent endpoints and verifies cryptographic signatures:

• JSONRPC - Validates JSON-RPC 2.0 compliance and connectivity
• GRPC - Tests gRPC endpoint accessibility
• REST - Verifies HTTP+JSON endpoint patterns
• JWS Signatures - Cryptographic verification of agent card authenticity (RFC 7515)
• Consistency - Ensures equivalent functionality across protocols

Perfect for testing your own agents and evaluating third-party agents before integration.

Signature Verification (New in v1.2.0)

CapiscIO CLI now includes secure by default JWS signature verification for agent cards:

🔐 Cryptographic Validation

• RFC 7515 compliant JWS (JSON Web Signature) verification
• JWKS (JSON Web Key Set) fetching from trusted sources
• Detached signature support for agent card authentication
• HTTPS-only JWKS endpoints for security

🛡️ Secure by Default

# Signature verification runs automatically
capiscio validate ./agent-card.json

# Opt-out when signatures aren't needed
capiscio validate ./agent-card.json --skip-signature

✅ Benefits

• Authenticity - Verify agent cards haven't been tampered with
• Trust - Cryptographically confirm the publisher's identity
• Security - Prevent malicious agent card injection
• Compliance - Meet security requirements for production deployments

Signature verification adds minimal overhead while providing crucial security guarantees for agent ecosystems.

CI/CD Integration

Using NPM Package:

# GitHub Actions
- name: Validate Agent
  run: |
    npm install -g capiscio-cli
    capiscio validate ./agent-card.json --json --strict

Using Standalone Binary (Core):

# GitHub Actions - No Node.js required
- name: Download and Validate Agent
  run: |
    # Download Core Binary (Linux AMD64)
    curl -L -o capiscio https://github.com/capiscio/capiscio-core/releases/download/v1.0.2/capiscio-linux-amd64
    chmod +x capiscio
    ./capiscio validate ./agent-card.json --json --strict

Exit codes: 0 = success, 1 = validation failed

FAQ

Q: What is the A2A Protocol?
A: The Agent-to-Agent (A2A) protocol v0.3.0 is a standardized specification for AI agent discovery, communication, and interoperability. Learn more at capisc.io.

Q: How is this different from schema validators?
A: We actually test live JSONRPC, GRPC, and REST endpoints with transport protocol validation, not just JSON schema structure. We also verify JWS signatures for cryptographic authenticity.

Q: Can I validate LLM agent cards?
A: Yes! Perfect for AI/LLM developers validating agent configurations and testing third-party agents before integration.

Q: What file formats are supported?
A: Current spec uses agent-card.json. We also support legacy agent.json files and auto-discover from /.well-known/agent-card.json endpoints.

License

Apache-2.0 © CapiscIO

Need help? Visit capisc.io | Open an issue | Documentation | Web Validator

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