Function flattenTopLevelComposition

src/utils/json-schema.ts:241–276

* Flattens a schema with top-level anyOf/oneOf/allOf to a simple object schema. * This is needed because some providers (OpenRouter, Claude) don't support * schema composition keywords at the top level of tool input schemas. * * @param schema - The schema to flatten * @returns A flattened schem

(schema: Record<string, unknown>)

 * @returns A flattened schema without top-level composition keywords
 */
function flattenTopLevelComposition(schema: Record<string, unknown>): Record<string, unknown> {
	const { anyOf, oneOf, allOf, ...rest } = schema

	// If no top-level composition keywords, return as-is
	if (!anyOf && !oneOf && !allOf) {
		return schema
	}

	// Get the composition array to process (prefer anyOf, then oneOf, then allOf)
	const compositionArray = (anyOf || oneOf || allOf) as Record<string, unknown>[] | undefined
	if (!compositionArray || !Array.isArray(compositionArray) || compositionArray.length === 0) {
		return schema
	}

	// Find the first non-null object type variant to use as the base
	// This preserves the most information while making the schema compatible
	const objectVariant = compositionArray.find(
		(variant) =>
			typeof variant === "object" &&
			variant !== null &&
			(variant.type === "object" || variant.properties !== undefined),
	)

	if (objectVariant) {
		// Merge remaining properties with the object variant
		return { ...rest, ...objectVariant }
	}

	// If no object variant found, create a generic object schema
	// This is a fallback that allows any object structure
	return {
		type: "object",
		additionalProperties: false,
		...rest,
	}
}

/**
 * Normalizes a tool input JSON Schema to be compliant with JSON Schema draft 2020-12.