OpenAI Agents empty tool arguments: Sume no-argument tools

Sume has tools that legitimately take no arguments, and they accept an empty JSON object {}. Paid tools cannot run empty: they require idempotency_key, so an empty or missing arguments payload cannot submit paid work.

OpenAI Agents Python 0.22.1 (2026-09-08) lists "fix(core): fail closed on empty tool arguments (#4545)". The release notes give no more detail, so this post does not guess what the SDK counts as empty. Sume side: MCP tools and gates and the MCP server code, read 2026-10-01.

Which Sume tools take no arguments?

In the server code, a shared empty schema (an object with no properties and none required) backs the read tools below. Discover the current set in a session with tools_list, and fetch one contract with tools_schema.

Does {} count as a valid payload for them?

Yes by schema: an object with no required keys is satisfied by {}. Object schemas also set additionalProperties: false, so the contract does not allow extra keys on a no-argument tool. If your SDK treats an empty string or missing arguments as a failure, send the literal {} for these tools.

What stops an empty call from spending money?

The gate table in the docs lists idempotency_key as required on write and paid tools: a stable key for transport and dedup, not human approval. A paid call with empty arguments has no key, so it fails validation instead of submitting. dry_run=true previews admission and cost without submitting, and max_spend_usd is enforced only when provided.

How do I test this in an agent?

Call tools_schema with name set to a tool you want to inspect, then run one no-argument read such as mcp_health with {} and one paid tool without a key, and confirm the second fails. For approval flows on top of validated arguments, see OpenAI Agents Python conditional approval with Sume dry run.