diff --git a/cmd/thv-operator/api/v1alpha1/virtualmcpcompositetooldefinition_types.go b/cmd/thv-operator/api/v1alpha1/virtualmcpcompositetooldefinition_types.go
index b8214c975..adff56749 100644
--- a/cmd/thv-operator/api/v1alpha1/virtualmcpcompositetooldefinition_types.go
+++ b/cmd/thv-operator/api/v1alpha1/virtualmcpcompositetooldefinition_types.go
@@ -46,6 +46,32 @@ type VirtualMCPCompositeToolDefinitionSpec struct {
// +kubebuilder:default=abort
// +optional
FailureMode string `json:"failureMode,omitempty"`
+
+ // OutputFormat is an optional Go template for constructing the workflow output.
+ // If specified, the template is evaluated with access to:
+ // - .params.* - Input parameters
+ // - .steps.*.output - Step outputs
+ // - .steps.*.status - Step status
+ // - .workflow.* - Workflow metadata (id, duration, timestamps)
+ //
+ // The template must produce valid JSON. If omitted, defaults to returning
+ // the last step's output (backward compatible behavior).
+ //
+ // Example:
+ // outputFormat: |
+ // {
+ // "data": {
+ // "logs": {{.steps.fetch_logs.output}},
+ // "metrics": {{.steps.fetch_metrics.output}}
+ // },
+ // "metadata": {
+ // "workflow_id": "{{.workflow.id}}",
+ // "duration_ms": {{.workflow.duration_ms}}
+ // }
+ // }
+ //
+ // +optional
+ OutputFormat string `json:"outputFormat,omitempty"`
}
// VirtualMCPCompositeToolDefinitionStatus defines the observed state of VirtualMCPCompositeToolDefinition
diff --git a/deploy/charts/operator-crds/Chart.yaml b/deploy/charts/operator-crds/Chart.yaml
index abb1ad542..beabb7094 100644
--- a/deploy/charts/operator-crds/Chart.yaml
+++ b/deploy/charts/operator-crds/Chart.yaml
@@ -2,5 +2,5 @@ apiVersion: v2
name: toolhive-operator-crds
description: A Helm chart for installing the ToolHive Operator CRDs into Kubernetes.
type: application
-version: 0.0.57
+version: 0.0.58
appVersion: "0.0.1"
diff --git a/deploy/charts/operator-crds/README.md b/deploy/charts/operator-crds/README.md
index 05cf6811c..039775afc 100644
--- a/deploy/charts/operator-crds/README.md
+++ b/deploy/charts/operator-crds/README.md
@@ -1,7 +1,7 @@
# ToolHive Operator CRDs Helm Chart
-
+
A Helm chart for installing the ToolHive Operator CRDs into Kubernetes.
diff --git a/deploy/charts/operator-crds/crds/toolhive.stacklok.dev_virtualmcpcompositetooldefinitions.yaml b/deploy/charts/operator-crds/crds/toolhive.stacklok.dev_virtualmcpcompositetooldefinitions.yaml
index ec84fd5c6..3e9fde065 100644
--- a/deploy/charts/operator-crds/crds/toolhive.stacklok.dev_virtualmcpcompositetooldefinitions.yaml
+++ b/deploy/charts/operator-crds/crds/toolhive.stacklok.dev_virtualmcpcompositetooldefinitions.yaml
@@ -92,6 +92,31 @@ spec:
minLength: 1
pattern: ^[a-z0-9]([a-z0-9_-]*[a-z0-9])?$
type: string
+ outputFormat:
+ description: |-
+ OutputFormat is an optional Go template for constructing the workflow output.
+ If specified, the template is evaluated with access to:
+ - .params.* - Input parameters
+ - .steps.*.output - Step outputs
+ - .steps.*.status - Step status
+ - .workflow.* - Workflow metadata (id, duration, timestamps)
+
+ The template must produce valid JSON. If omitted, defaults to returning
+ the last step's output (backward compatible behavior).
+
+ Example:
+ outputFormat: |
+ {
+ "data": {
+ "logs": {{.steps.fetch_logs.output}},
+ "metrics": {{.steps.fetch_metrics.output}}
+ },
+ "metadata": {
+ "workflow_id": "{{.workflow.id}}",
+ "duration_ms": {{.workflow.duration_ms}}
+ }
+ }
+ type: string
parameters:
additionalProperties:
description: ParameterSpec defines a parameter for a composite tool
diff --git a/docs/operator/crd-api.md b/docs/operator/crd-api.md
index b857221cc..1639cbfb3 100644
--- a/docs/operator/crd-api.md
+++ b/docs/operator/crd-api.md
@@ -1813,6 +1813,7 @@ _Appears in:_
| `steps` _[WorkflowStep](#workflowstep) array_ | Steps defines the workflow step definitions
Steps are executed sequentially in Phase 1
Phase 2 will support DAG execution via dependsOn | | MinItems: 1
Required: \{\}
|
| `timeout` _string_ | Timeout is the overall workflow timeout
Defaults to 30m if not specified | 30m | Pattern: `^([0-9]+(\.[0-9]+)?(ms\|s\|m\|h))+$`
|
| `failureMode` _string_ | FailureMode defines the failure handling strategy
- abort: Stop execution on first failure (default)
- continue: Continue executing remaining steps
- best_effort: Try all steps, report partial success | abort | Enum: [abort continue best_effort]
|
+| `outputFormat` _string_ | OutputFormat is an optional Go template for constructing the workflow output.
If specified, the template is evaluated with access to:
- .params.* - Input parameters
- .steps.*.output - Step outputs
- .steps.*.status - Step status
- .workflow.* - Workflow metadata (id, duration, timestamps)
The template must produce valid JSON. If omitted, defaults to returning
the last step's output (backward compatible behavior).
Example:
outputFormat: \|
\{
"data": \{
"logs": \{\{.steps.fetch_logs.output\}\},
"metrics": \{\{.steps.fetch_metrics.output\}\}
\},
"metadata": \{
"workflow_id": "\{\{.workflow.id\}\}",
"duration_ms": \{\{.workflow.duration_ms\}\}
\}
\} | | |
#### VirtualMCPCompositeToolDefinitionStatus
diff --git a/pkg/vmcp/composer/composer.go b/pkg/vmcp/composer/composer.go
index 031159b55..febdfafe2 100644
--- a/pkg/vmcp/composer/composer.go
+++ b/pkg/vmcp/composer/composer.go
@@ -59,6 +59,17 @@ type WorkflowDefinition struct {
// Options: "abort" (default), "continue", "best_effort"
FailureMode string
+ // OutputFormat is an optional Go template for constructing the workflow output.
+ // If specified, the template is evaluated with access to:
+ // - .params.* - Input parameters
+ // - .steps.*.output - Step outputs
+ // - .steps.*.status - Step status
+ // - .workflow.* - Workflow metadata (id, duration, timestamps)
+ //
+ // The template must produce valid JSON. If omitted, defaults to returning
+ // the last step's output (backward compatible behavior).
+ OutputFormat string
+
// Metadata stores additional workflow information.
Metadata map[string]string
}
diff --git a/pkg/vmcp/config/config.go b/pkg/vmcp/config/config.go
index 56de900cc..e4ce03ec4 100644
--- a/pkg/vmcp/config/config.go
+++ b/pkg/vmcp/config/config.go
@@ -339,6 +339,30 @@ type CompositeToolConfig struct {
// Steps are the workflow steps to execute.
Steps []*WorkflowStepConfig `json:"steps"`
+
+ // OutputFormat is an optional template for constructing the workflow output.
+ // If specified, the template is evaluated with access to:
+ // - .params.* - Input parameters
+ // - .steps.*.output - Step outputs
+ // - .steps.*.status - Step status
+ // - .workflow.* - Workflow metadata (id, duration, timestamps)
+ //
+ // The template must produce valid JSON. If omitted, defaults to returning
+ // the last step's output (backward compatible behavior).
+ //
+ // Example:
+ // output_format: |
+ // {
+ // "data": {
+ // "logs": {{.steps.fetch_logs.output}},
+ // "metrics": {{.steps.fetch_metrics.output}}
+ // },
+ // "metadata": {
+ // "workflow_id": "{{.workflow.id}}",
+ // "duration_ms": {{.workflow.duration_ms}}
+ // }
+ // }
+ OutputFormat string `json:"output_format,omitempty" yaml:"output_format,omitempty"`
}
// ParameterSchema defines a workflow parameter.
diff --git a/pkg/vmcp/server/workflow_converter.go b/pkg/vmcp/server/workflow_converter.go
index f8d0fb5d9..30d4381aa 100644
--- a/pkg/vmcp/server/workflow_converter.go
+++ b/pkg/vmcp/server/workflow_converter.go
@@ -75,12 +75,13 @@ func ConvertConfigToWorkflowDefinitions(
// Create workflow definition
def := &composer.WorkflowDefinition{
- Name: ct.Name,
- Description: ct.Description,
- Parameters: params,
- Steps: steps,
- Timeout: timeout,
- Metadata: make(map[string]string),
+ Name: ct.Name,
+ Description: ct.Description,
+ Parameters: params,
+ Steps: steps,
+ Timeout: timeout,
+ OutputFormat: ct.OutputFormat,
+ Metadata: make(map[string]string),
}
workflowDefs[ct.Name] = def
diff --git a/pkg/vmcp/server/workflow_converter_test.go b/pkg/vmcp/server/workflow_converter_test.go
index 595ac2327..0142734bb 100644
--- a/pkg/vmcp/server/workflow_converter_test.go
+++ b/pkg/vmcp/server/workflow_converter_test.go
@@ -264,3 +264,89 @@ func TestConvertSteps_ComplexWorkflow(t *testing.T) {
assert.NotEmpty(t, result[2].Condition)
assert.Equal(t, []string{"confirm"}, result[2].DependsOn)
}
+
+func TestConvertConfigToWorkflowDefinitions_WithOutputFormat(t *testing.T) {
+ t.Parallel()
+
+ tests := []struct {
+ name string
+ input []*config.CompositeToolConfig
+ wantOutputFormat string
+ }{
+ {
+ name: "workflow without output_format",
+ input: []*config.CompositeToolConfig{{
+ Name: "simple",
+ Steps: []*config.WorkflowStepConfig{
+ {ID: "s1", Type: "tool", Tool: "backend.tool"},
+ },
+ }},
+ wantOutputFormat: "",
+ },
+ {
+ name: "workflow with output_format",
+ input: []*config.CompositeToolConfig{{
+ Name: "aggregated",
+ Steps: []*config.WorkflowStepConfig{
+ {ID: "fetch_logs", Type: "tool", Tool: "splunk.fetch"},
+ {ID: "fetch_metrics", Type: "tool", Tool: "datadog.fetch"},
+ },
+ OutputFormat: `{
+ "logs": {{.steps.fetch_logs.output}},
+ "metrics": {{.steps.fetch_metrics.output}}
+ }`,
+ }},
+ wantOutputFormat: `{
+ "logs": {{.steps.fetch_logs.output}},
+ "metrics": {{.steps.fetch_metrics.output}}
+ }`,
+ },
+ {
+ name: "workflow with complex output_format",
+ input: []*config.CompositeToolConfig{{
+ Name: "investigation",
+ Steps: []*config.WorkflowStepConfig{
+ {ID: "fetch_data", Type: "tool", Tool: "backend.fetch"},
+ {ID: "analyze", Type: "tool", Tool: "backend.analyze"},
+ },
+ OutputFormat: `{
+ "data": {{.steps.fetch_data.output}},
+ "analysis": {{.steps.analyze.output}},
+ "metadata": {
+ "workflow_id": "{{.workflow.id}}",
+ "duration_ms": {{.workflow.duration_ms}}
+ }
+ }`,
+ }},
+ wantOutputFormat: `{
+ "data": {{.steps.fetch_data.output}},
+ "analysis": {{.steps.analyze.output}},
+ "metadata": {
+ "workflow_id": "{{.workflow.id}}",
+ "duration_ms": {{.workflow.duration_ms}}
+ }
+ }`,
+ },
+ }
+
+ for _, tt := range tests {
+ t.Run(tt.name, func(t *testing.T) {
+ t.Parallel()
+
+ result, err := ConvertConfigToWorkflowDefinitions(tt.input)
+
+ require.NoError(t, err)
+ require.Len(t, result, 1)
+
+ // Get the first (and only) workflow definition
+ var workflowDef *composer.WorkflowDefinition
+ for _, def := range result {
+ workflowDef = def
+ break
+ }
+
+ require.NotNil(t, workflowDef)
+ assert.Equal(t, tt.wantOutputFormat, workflowDef.OutputFormat)
+ })
+ }
+}