micro/go-micro · error

a2a %s: %s (%d)

Error message

a2a %s: %s (%d)

What it means

call is the generic JSON-RPC invoker used by SendMessage, SetPushNotificationConfig, and PushNotificationConfig. The library throws this error when the HTTP response decodes successfully but carries a non-null JSON-RPC error object, formatting it as 'a2a <method>: <message> (<code>)'. It distinguishes application-level rejections from transport failures.

Source

Thrown at gateway/a2a/client.go:263

	if err != nil {
		return nil, err
	}
	req.Header.Set("Content-Type", "application/json")
	resp, err := c.http.Do(req)
	if err != nil {
		return nil, err
	}
	defer resp.Body.Close()

	var out struct {
		Result json.RawMessage `json:"result"`
		Error  *rpcError       `json:"error"`
	}
	if err := json.NewDecoder(resp.Body).Decode(&out); err != nil {
		return nil, err
	}
	if out.Error != nil {
		return nil, fmt.Errorf("a2a %s: %s (%d)", method, out.Error.Message, out.Error.Code)
	}
	return out.Result, nil
}

func terminal(state string) bool {
	switch state {
	case "completed", "failed", "canceled", "rejected", "input-required":
		return true
	}
	return false
}

func artifactsText(arts []Artifact) string {
	var parts []Part
	for _, a := range arts {
		parts = append(parts, a.Parts...)
	}
	return textOf(parts)

View on GitHub (pinned to 24529f1404)

Solutions

1. Map the JSON-RPC code: -32601 method not found (spec/agent version mismatch), -32602 invalid params (fix payload), task-not-found codes (re-send or poll), auth codes (fix credentials).
2. Compare your client and agent A2A protocol versions; upgrade the client or pin the agent to a compatible version.
3. Validate Message Parts and push notification config fields before sending.
4. Retry only for transient server-side codes; do not retry invalid-param or not-found errors.

result, err := c.SendMessage(ctx, msg)
if err != nil {
	if m := rpcRe.FindStringSubmatch(err.Error()); m != nil {
		method, message, code := m[1], m[2], m[3]
		switch code {
		case "-32601": // method not found: version mismatch
		case "-32602": // invalid params: fix payload
		}
	}
	return err
}

When it happens

Trigger: Any of the call-based methods (SendMessage, SetPushNotificationConfig, PushNotificationConfig) receives a JSON-RPC error frame: method not found, invalid params (malformed Message/Part or push config), task not found, or unauthorized.

Common situations: Agent implements an older A2A spec lacking a method the client calls; Message Parts use a kind the agent rejects; push notification config references an unknown task; API key/credential invalid at the agent.

Related errors

• a2a tasks/resubscribe: %s (%d)
• ${rsp.Status}: ${body} (dynamic HTTP status and body)
• no response from API
• no response from API
• no response from API

AI-assisted analysis of micro/go-micro@24529f1404 (2026-09-01). Data as JSON: /api/errors/d59aac93447359d9. Report an issue: GitHub.