API Reference - CoinFello Docs

A2A Endpoint

CoinFello exposes a single API endpoint that implements the Agent-to-Agent protocol spec over JSON-RPC 2.0.

POST https://app.coinfello.com/api/a2a

Methods

Method	Description
`message/send`	Send a message and get a response
`message/stream`	Send a message and stream the response via SSE
`tasks/get`	Get a task by ID (optionally limit history with `historyLength`)
`tasks/cancel`	Cancel a running task

Agent ID

Every message/send and message/stream request must include an agentId so the endpoint knows which agent to route the message to. The endpoint is agent-agnostic — there is no hardcoded default. Pass the agentId (a number) in params.configuration:

{
  "params": {
    "configuration": { "agentId": 1 },
    "message": { ... }
  }
}

Omitting the agentId on a new request returns an error: "agentId is required: provide in configuration.agentId or as a DataPart". Subsequent messages that reference an existing taskId do not need to repeat it. Retrieve the agent’s numeric ID from the agent card under skills where each entry is a separate chat agent.

Send a Message

curl -b cookies.txt -X POST https://app.coinfello.com/api/a2a \
  -H "Content-Type: application/json" \
  -d '{
    "jsonrpc": "2.0",
    "id": 1,
    "method": "message/send",
    "params": {
      "configuration": { "agentId": 1 },
      "message": {
        "role": "user",
        "parts": [{ "type": "text", "text": "What are the best yields for ETH right now?" }]
      }
    }
  }'

Stream a Response

Use message/stream to receive Server-Sent Events. Each SSE data line is a JSON-RPC response wrapping an A2A stream event.

curl -b cookies.txt -X POST https://app.coinfello.com/api/a2a \
  -H "Content-Type: application/json" \
  -d '{
    "jsonrpc": "2.0",
    "id": 1,
    "method": "message/stream",
    "params": {
      "configuration": { "agentId": 1 },
      "message": {
        "role": "user",
        "parts": [{ "type": "text", "text": "Swap 0.1 ETH to USDC" }]
      }
    }
  }'

Get a Task

curl -X POST https://app.coinfello.com/api/a2a \
  -H "Content-Type: application/json" \
  -d '{
    "jsonrpc": "2.0",
    "id": 1,
    "method": "tasks/get",
    "params": { "id": "task-id-here", "historyLength": 5 }
  }'

Cancel a Task

curl -X POST https://app.coinfello.com/api/a2a \
  -H "Content-Type: application/json" \
  -d '{
    "jsonrpc": "2.0",
    "id": 1,
    "method": "tasks/cancel",
    "params": { "id": "task-id-here" }
  }'

Authentication

Authentication uses SIWE (Sign-In with Ethereum). Complete the SIWE flow to obtain a session cookie before making requests. Unauthenticated requests return a 401 error. See the Authentication page for the full SIWE flow with curl examples.

Errors

Errors follow standard JSON-RPC 2.0 error format:

Code	Meaning
`-32600`	Invalid JSON-RPC request
`-32601`	Unknown method
`-32001`	Task not found
`-32002`	Task not cancelable
`-32603`	Internal server error

Rate Limits

API requests are rate-limited. Current limits are provided in response headers:

Header	Description
`X-RateLimit-Limit`	Maximum requests per minute
`X-RateLimit-Remaining`	Requests remaining in current window
`X-RateLimit-Reset`	Unix timestamp when the window resets

​A2A Endpoint

​Methods

​Agent ID

​Send a Message

​Stream a Response

​Get a Task

​Cancel a Task

​Authentication

​Errors

​Rate Limits