Function coerceToolResult

packages/agent-core/src/loop/tool-call.ts:619–637

* Validate a tool's raw return against the ExecutableToolResult contract. * A tool that returns `undefined`, a primitive, or an object without a valid * `output` field is coerced into an `isError: true` result so the loop can still * emit a paired `tool.result` event. This is the trust bo

(value: unknown, toolName: string)

 * arbitrary tool implementations and the rest of the loop.
 */
function coerceToolResult(value: unknown, toolName: string): ExecutableToolResult {
  if (value === null || value === undefined) {
    return { output: `Tool "${toolName}" returned no result.`, isError: true };
  }
  if (typeof value !== 'object') {
    return {
      output: `Tool "${toolName}" returned a ${typeof value} instead of a tool result.`,
      isError: true,
    };
  }
  const candidate = value as { output?: unknown };
  if (typeof candidate.output !== 'string' && !Array.isArray(candidate.output)) {
    return {
      output: `Tool "${toolName}" returned a result with a missing or malformed "output" field.`,
      isError: true,
    };
  }
  return value as ExecutableToolResult;
}

function normalizeToolResult(r: ExecutableToolResult): ExecutableToolResult {
  let output: ExecutableToolResult['output'];