Capability Discovery Pattern

Overview

For agents to collaborate effectively, each needs to understand what others can do. The Capability Discovery Pattern provides mechanisms for agents to advertise their abilities and discover suitable collaborators.

Discovery Mechanisms

Agent Cards (A2A Protocol)

{
  "name": "TranslationAgent",
  "version": "2.0",
  "capabilities": [
    {
      "skill": "translate",
      "languages": ["en", "es", "fr", "de", "zh"],
      "max_tokens": 10000
    }
  ],
  "endpoint": "https://agent.example.com/a2a",
  "authentication": ["oauth2", "api_key"]
}

MCP Tool Lists

{
  "tools": [{
    "name": "query_database",
    "description": "Execute SQL queries",
    "inputSchema": {...}
  }]
}

DID-Based Discovery (ANP)

Decentralized capability graphs using JSON-LD and W3C DIDs.

Discovery Patterns

Static Registry

Agents register in a central directory:

┌─────────────┐
│  Registry   │
│  ┌───────┐  │
│  │Agent A│  │
│  │Agent B│  │
│  │Agent C│  │
│  └───────┘  │
└──────┬──────┘
       │
   Query: "Who can translate?"
       │
   Response: [Agent A, Agent C]

Well-Known Endpoints

Agents publish capability documents at standard URLs:

https://agent.example.com/.well-known/agent.json

Peer-to-Peer Broadcast

In decentralized networks, agents broadcast capabilities and maintain local caches.

Semantic Matching

Use embedding similarity to match requests to capabilities:

request_embedding = embed("translate legal document to Spanish")
for agent in agents:
    similarity = cosine_sim(request_embedding, agent.capability_embedding)
    if similarity > threshold:
        candidates.append(agent)

Negotiation Protocols

After discovery, agents negotiate collaboration terms:

Capability Verification

Request proof of claimed capabilities:

Requester: Can you translate this test sentence?
Provider: [Demonstrates capability]
Requester: Verified. Proceeding with task.

Parameter Negotiation

Agree on task parameters:

{
  "proposed": {"format": "markdown", "length": "detailed"},
  "counter": {"format": "plain_text", "length": "detailed"},
  "agreed": {"format": "plain_text", "length": "detailed"}
}

Resource Negotiation

Agree on resource constraints:

• Maximum execution time
• Token budgets
• Cost limits

Security Considerations

Capability Spoofing

Malicious agents may exaggerate capabilities. Defenses:

• Signed capability attestations
• Reputation systems
• Verification challenges

Discovery Spam

Agents may flood discovery systems. Defenses:

• Rate limiting
• Stake-based registration
• Proof-of-work challenges

Implementation Tips

• Cache discovery results with TTL
• Implement fallback agents for critical capabilities
• Monitor capability usage patterns for optimization
• Version capability schemas for backward compatibility