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test(mcp): reject narrowing optional additions #4

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Merged
barbatdev merged 1 commit into from
Aug 31, 2026
Merged

test(mcp): reject narrowing optional additions #4

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15 changes: 12 additions & 3 deletions internal/mcp/tool_contract_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -381,6 +381,11 @@ func TestCompareMCPToolContract(t *testing.T) {
if err := compareMCPToolContract(additionalBase, base); err == nil || !strings.Contains(err.Error(), "additional-properties-narrowed") {
t.Fatalf("additionalProperties narrowing error = %v", err)
}
permissiveBase := map[string]mcpToolSchema{"x": {Types: []string{"object"}, Additional: true}}
permissiveLive := map[string]mcpToolSchema{"x": {Types: []string{"object"}, Properties: map[string]mcpToolSchema{"new": {Types: []string{"boolean"}}}, Additional: true}}
if err := compareMCPToolContract(permissiveBase, permissiveLive); err == nil || !strings.Contains(err.Error(), "/tools/x/properties/new: additional-properties-narrowed") {
t.Fatalf("permissive additionalProperties optional addition error = %v", err)
}
}

func TestCompareMCPToolContractDiagnostics(t *testing.T) {
Expand Down Expand Up @@ -423,7 +428,7 @@ func TestMCPToolContractV1(t *testing.T) {
}

func TestVerifyMCPToolContract(t *testing.T) {
fixture := map[string]mcpToolSchema{"base": {Types: []string{"object"}, Properties: map[string]mcpToolSchema{"kept": {Types: []string{"string"}}}, Additional: true}}
fixture := map[string]mcpToolSchema{"base": {Types: []string{"object"}, Properties: map[string]mcpToolSchema{"kept": {Types: []string{"string"}}}, Additional: false}}
canonical := []byte(formatMCPToolContract(fixture))
live := map[string]mcpToolSchema{"base": {Types: []string{"object"}, Properties: map[string]mcpToolSchema{"kept": {Types: []string{"string"}}, "added": {Types: []string{"boolean"}}}, Additional: true}, "new": {Types: []string{"string"}}}
if err := verifyMCPToolContract(fixture, live, canonical); err != nil {
Expand Down Expand Up @@ -646,8 +651,12 @@ func compareMCPToolSchema(drifts *[]mcpToolContractDrift, path string, v1, live
}
}
for _, name := range sortedKeys(live.Properties) {
if _, exists := v1.Properties[name]; !exists && !slices.Contains(live.Required, name) && !simplePrimitive(live.Properties[name]) {
driftAt(drifts, jsonPointer(jsonPointer(path, "properties"), name), "unproven-optional-addition", mcpToolSchema{}, live.Properties[name])
if _, exists := v1.Properties[name]; !exists && !slices.Contains(live.Required, name) {
if v1.Additional {
driftAt(drifts, jsonPointer(jsonPointer(path, "properties"), name), "additional-properties-narrowed", mcpToolSchema{}, live.Properties[name])
} else if !simplePrimitive(live.Properties[name]) {
driftAt(drifts, jsonPointer(jsonPointer(path, "properties"), name), "unproven-optional-addition", mcpToolSchema{}, live.Properties[name])
}
}
}
}
Expand Down
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