fix(mcp): accept agent_id on create_card

- the agent MCP client injects agent_id into every call; create_card
  alone lacked the field, so the strict (additionalProperties:false)
  schema rejected the orchestrator's subtask creation with
  "unexpected additional properties [agent_id]"
- add agent_id for parity with the other card tools; regression test

Author: mhersson

internal/mcp/server_test.go

@@ -225,6 +225,31 @@ func TestCreateAndGetCard(t *testing.T) {
 	assert.Equal(t, created.Priority, fetched.Priority)
 }
 
+// The agent MCP client injects agent_id into every call (universal
+// attribution). create_card must accept it like the other card tools, or the
+// orchestrator's subtask creation is rejected at schema validation with
+// "unexpected additional properties [agent_id]".
+func TestCreateCardAcceptsAgentID(t *testing.T) {
+	env := setupMCP(t)
+
+	result, err := env.session.CallTool(context.Background(), &mcp.CallToolParams{
+		Name: "create_card",
+		Arguments: map[string]any{
+			"project":  "test-project",
+			"title":    "Subtask from agent",
+			"type":     "task",
+			"priority": "medium",
+			"agent_id": "cmx-agent-test-001",
+		},
+	})
+	require.NoError(t, err, "create_card must accept agent_id (the agent injects it on every call)")
+	require.False(t, result.IsError, "create_card with agent_id should not error")
+
+	var card board.Card
+	unmarshalResult(t, result, &card)
+	assert.Equal(t, "Subtask from agent", card.Title)
+}
+
 func TestUpdateCard(t *testing.T) {
 	env := setupMCP(t)
 

internal/mcp/tools_cards.go

@@ -44,6 +44,12 @@ type createCardInput struct {
 	Body      string    `json:"body,omitempty" jsonschema:"optional markdown body"`
 	Parent    string    `json:"parent,omitempty" jsonschema:"parent card ID for subtasks"`
 	DependsOn []string  `json:"depends_on,omitempty" jsonschema:"card IDs this depends on"`
+	// AgentID is accepted for parity with the other card tools: the agent MCP
+	// client injects agent_id into every call, so create_card must declare it or
+	// the strict (additionalProperties:false) schema rejects the orchestrator's
+	// subtask creation. Not threaded to attribution today (the service has no
+	// author param); present so the call validates.
+	AgentID string `json:"agent_id,omitempty" jsonschema:"caller identity (accepted for client parity; not used for attribution)"`
 }
 
 // NOTE: vetted, autonomous, feature_branch, create_pr, and model pin fields