A2A Server

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OmniRoute A2A Server Documentation

Agent-to-Agent Protocol v0.3 — OmniRoute as an intelligent routing agent

The A2A surface has two faces:

• JSON-RPC 2.0 at POST /a2a (canonical entry point, defined in src/app/a2a/route.ts).
• REST under /api/a2a/* for dashboards and tooling (status, task list, cancel).

Tasks are tracked by A2ATaskManager (src/lib/a2a/taskManager.ts, default 5-minute TTL). Skills are dispatched via A2A_SKILL_HANDLERS in src/lib/a2a/taskExecution.ts.

Agent Discovery

curl http://localhost:20128/.well-known/agent.json

Returns the Agent Card describing OmniRoute's capabilities, skills, and authentication requirements.

The Agent Card's version field is sourced from process.env.npm_package_version (see src/app/.well-known/agent.json/route.ts:13), so it stays auto-synced with package.json on every release.

---

Authentication

All /a2a requests require an API key via the Authorization header:

Authorization: Bearer YOUR_OMNIROUTE_API_KEY

If no API key is configured on the server, authentication is bypassed.

Enablement

A2A is controlled by the Endpoints → A2A toggle and is disabled by default. When disabled, GET /api/a2a/status reports status: "disabled" and online: false; JSON-RPC calls to POST /a2a return HTTP 503 with JSON-RPC error code -32000.

---

JSON-RPC 2.0 Methods

message/send — Synchronous Execution

Sends a message to a skill and waits for the complete response.

curl -X POST http://localhost:20128/a2a \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer YOUR_KEY" \
  -d '{
    "jsonrpc": "2.0",
    "id": "1",
    "method": "message/send",
    "params": {
      "skill": "smart-routing",
      "messages": [{"role": "user", "content": "Write a hello world in Python"}],
      "metadata": {"model": "auto", "combo": "fast-coding"}
    }
  }'

Response:

{
  "jsonrpc": "2.0",
  "id": "1",
  "result": {
    "task": { "id": "uuid", "state": "completed" },
    "artifacts": [{ "type": "text", "content": "..." }],
    "metadata": {
      "routing_explanation": "Selected claude-sonnet via provider \"anthropic\" (latency: 1200ms, cost: $0.003)",
      "cost_envelope": { "estimated": 0.005, "actual": 0.003, "currency": "USD" },
      "resilience_trace": [
        { "event": "primary_selected", "provider": "anthropic", "timestamp": "..." }
      ],
      "policy_verdict": { "allowed": true, "reason": "within budget and quota limits" }
    }
  }
}

message/stream — SSE Streaming

Same as message/send but returns Server-Sent Events for real-time streaming.

curl -N -X POST http://localhost:20128/a2a \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer YOUR_KEY" \
  -d '{
    "jsonrpc": "2.0",
    "id": "1",
    "method": "message/stream",
    "params": {
      "skill": "smart-routing",
      "messages": [{"role": "user", "content": "Explain quantum computing"}]
    }
  }'

SSE Events:

data: {"jsonrpc":"2.0","method":"message/stream","params":{"task":{"id":"...","state":"working"},"chunk":{"type":"text","content":"..."}}}

: heartbeat 2026-03-03T17:00:00Z

data: {"jsonrpc":"2.0","method":"message/stream","params":{"task":{"id":"...","state":"completed"},"metadata":{...}}}

tasks/get — Query Task Status

curl -X POST http://localhost:20128/a2a \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer YOUR_KEY" \
  -d '{"jsonrpc":"2.0","id":"2","method":"tasks/get","params":{"taskId":"TASK_UUID"}}'

tasks/cancel — Cancel a Task

curl -X POST http://localhost:20128/a2a \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer YOUR_KEY" \
  -d '{"jsonrpc":"2.0","id":"3","method":"tasks/cancel","params":{"taskId":"TASK_UUID"}}'

---

Available Skills

OmniRoute exposes 5 A2A skills wired in src/lib/a2a/taskExecution.ts::A2A_SKILL_HANDLERS. Each skill module lives in src/lib/a2a/skills/.

Skill	ID	Description
Smart Routing	smart-routing	Routes a prompt through the optimal provider/combo using OmniRoute's combo engine + scoring
Quota Management	quota-management	Reports per-provider quota state, helps callers decide when to throttle/switch
Provider Discovery	provider-discovery	Lists installed providers with capabilities, free-tier flags, OAuth status
Cost Analysis	cost-analysis	Estimates cost of a request/conversation given the catalog + recent usage
Health Report	health-report	Aggregates circuit breaker, cooldown, lockout state per provider

Note: the Agent Card description currently advertises "36+ providers" (src/app/.well-known/agent.json/route.ts:26 and :55). The actual catalog has grown to 180+ providers — the string should be updated in a follow-up change (tracked as a separate doc/code TODO; not modified here).

---

REST API (auxiliary)

The JSON-RPC endpoint /a2a is the canonical A2A entry point. The REST endpoints below provide auxiliary access for dashboards and external tooling:

Endpoint	Method	Description	Auth
/api/a2a/status	GET	Server status, registered skills	(public)
/api/a2a/tasks	GET	List tasks with filters	management
/api/a2a/tasks/[id]	GET	Get task by ID	management
/api/a2a/tasks/[id]/cancel	POST	Cancel running task	management
/.well-known/agent.json	GET	Agent Card (A2A discovery)	(public, cached 3600s)

---

Adding a New Skill

1. Create skill file: src/lib/a2a/skills/<your-skill>.ts

   Export an async function (task: A2ATask) => Promise<{ artifacts, metadata }>. Follow the shape of existing skills such as smartRouting.ts.

2. Register handler: in src/lib/a2a/taskExecution.ts, add an entry to A2A_SKILL_HANDLERS:

   export const A2A_SKILL_HANDLERS = {
     // ...existing skills
     "your-skill": async (task) => {
       const skillModule = await import("./skills/yourSkill");
       return skillModule.executeYourSkill(task);
     },
   };

3. Expose in Agent Card: in src/app/.well-known/agent.json/route.ts, append to the skills array:

   {
     "id": "your-skill",
     "name": "Your Skill",
     "description": "Brief, intent-focused description",
     "tags": ["routing", "quota"],
     "examples": ["Sample natural-language invocation"]
   }

4. Write tests: tests/unit/a2a-<your-skill>.test.ts. Cover happy path + error path.

5. Document the new skill in this file's Available Skills table.

---

Task TTL

Tasks expire after ttlMinutes (default 5 min) — configured in the A2ATaskManager constructor at src/lib/a2a/taskManager.ts:82. To customize, fork the A2ATaskManager instantiation and pass a different value (e.g., new A2ATaskManager(15) for 15-minute TTL). A background interval sweeps expired tasks every 60 seconds.

---

Task Lifecycle

submitted → working → completed
                    → failed
                    → cancelled

• Tasks expire after 5 minutes by default (see Task TTL)
• Terminal states: completed, failed, cancelled
• Event log tracks every state transition

---

Error Codes

Code	Meaning
-32700	Parse error (invalid JSON)
-32600	Invalid request / Unauthorized
-32601	Method or skill not found
-32602	Invalid params
-32603	Internal error
-32000	A2A endpoint is disabled

---

Integration Examples

Python (requests)

import requests

resp = requests.post("http://localhost:20128/a2a", json={
    "jsonrpc": "2.0", "id": "1",
    "method": "message/send",
    "params": {
        "skill": "smart-routing",
        "messages": [{"role": "user", "content": "Hello"}]
    }
}, headers={"Authorization": "Bearer YOUR_KEY"})

result = resp.json()["result"]
print(result["artifacts"][0]["content"])
print(result["metadata"]["routing_explanation"])

TypeScript (fetch)

const resp = await fetch("http://localhost:20128/a2a", {
  method: "POST",
  headers: {
    "Content-Type": "application/json",
    Authorization: "Bearer YOUR_KEY",
  },
  body: JSON.stringify({
    jsonrpc: "2.0",
    id: "1",
    method: "message/send",
    params: {
      skill: "smart-routing",
      messages: [{ role: "user", content: "Hello" }],
    },
  }),
});
const { result } = await resp.json();
console.log(result.metadata.routing_explanation);