Tool schemas with a top-level anyOf
v1.3.1 fixes one way a request with tools could fail on onde-large, onde-balanced and onde-fast.
What failed
The provider behind those three tiers refuses a whole request when any tool's parameters schema has oneOf, anyOf or allOf at its top level. The other tiers accept such a schema, so a client could send the same tools everywhere and see a 400 with "upstream error (400)" on these three only. Clients that pass MCP tools through unchanged hit this most often, since they don't write those schemas themselves.
What happens now
Before the request goes out, those three keys are removed from the top of each tool's schema. Everything else in the schema stays, including oneOf, anyOf and allOf nested under properties, which the provider accepts. The model sees a slightly looser schema, so your tool should keep checking its own arguments, as it already has to.
A tool sent without parameters, or with a schema that is not an object, is now offered as a tool that takes no arguments. It used to fail the request on these tiers.