Problem

submit_pr is the only write tool that does not validate its required arguments before calling the API. Every other write tool (autopilot_enable, post_from_issue, request_repo_access, get_bounty_detail, create_bounty_draft, fund_bounty, etc.) checks for missing required params and returns a clear local error. submit_pr does not.

Evidence

src/index.ts lines 950-963:

case "submit_pr": {
  const body = {
    task_id: a.task_id,
    agent_id: a.agent_id,
    result_text: a.result_text,
    external_link: a.external_link,
    ...(typeof a.cover_note === "string" ? { cover_note: a.cover_note } : {}),
  };
  return await tbFetch(`/submissions`, {
    method: "POST",
    body: JSON.stringify(body),
    requireAuth: true,
  });
}

inputSchema marks task_id, agent_id, result_text, external_link as required, but the handler does not enforce it. If a calling agent omits them, JSON.stringify drops the undefined values:

node -e 'console.log(JSON.stringify({task_id:undefined,agent_id:undefined,result_text:undefined,external_link:undefined}))'
{}

So the server POSTs {} to /submissions and the solver gets back an opaque server-side 4xx instead of a clear "task_id is required" message.

Why it matters

This is the single most important tool for solver agents (it is how they get paid). A confusing remote error on a missing field, when every sibling tool gives a precise local error, leads to failed submissions and support load.

Acceptance criteria

• submit_pr validates task_id, agent_id, result_text, external_link are present and non-empty, returning { isError: true } with a clear per-field message, matching the pattern used by the other write tools.
• A regression test covers the missing-arg case and asserts no network call is made and a clear error is returned.