[Moonshot / MCP] kimi rejects MCP tool schemas with untyped anyOf unions (properties.freq: type)

## Observed symptom [Bug]: Moonshot (kimi-k3) rejects MCP tool schemas with untyped anyOf unions: "properties.freq: type is not defined" ### Describe the bug When the active model is served by Moonshot (`kimi-cn` / `kimi-intl` provider, e.g. `kimi-k3`), any agent turn that carries MCP tools whose parameter schema uses a **non-nullable `anyOf` union without a top-level `type`** fails with HTTP 400 before the model is even called: ``` Model 'kimi-k3' execution failed. Reason: Invalid request: tools.function.parameters is not a valid moonshot flavored json schema, details: <At path 'properties.freq': type is not defined> ``` The offending schema shape (emitted by several MCP servers to tolerate LLM mis-serialization of `string | integer`) looks like: ```json "freq": { "anyOf": [{"type": "string"}, {"type": "integer"}], "description": "分钟频度", "enum": ["1min", "5min", "15min", "30min", "60min"] } ``` Moonshot's "flavo ## Literal error text ``` properties.freq: type ``` ## Environment GitHub issue agentscope-ai/QwenPaw #7959; state=open ## Trigger / context ### Describe the bug When the active model is served by Moonshot (`kimi-cn` / `kimi-intl` provider, e.g. `kimi-k3`), any agent turn that carries MCP tools whose parameter schema uses a **non-nullable `anyOf` union without a top-level `type`** fails with HTTP 400 before the model is even called: ``` Model 'kimi-k3' execution failed. Reason: Invalid request: tools.function.parameters is not a valid moonshot flavored json schema, details: <At path 'properties.freq': type is not defined> ``` The offending schema shape (emitted by several MCP servers to tolerate LLM mis-serialization of `string | integer`) looks like: ```json "freq": { "anyOf": [{"type": "string"}, {"type": "integer"}], "description": "分钟频度", "enum": ["1min", "5min", "15min", "30min", "60min"] } ``` Moonshot's "flavored JSON schema" validator requires an explicit `type` on every property node and does not accept `anyOf`-only nodes. Because the whole `tools[]` array is rejected, the agent cannot make **any** call once such a tool is registered — the failure is not limited to the tool with the bad field. ### Root cause (from reading `qwenpaw/providers/openai_chat_model_compat.py`) `_apply_openai_compat_schema_passes` runs four passes: `$ref` inlining → boolean-schema sanitizing → **nullable** sanitizing → regex shorthand expansion. The nullable pass (`_sanitize_nullable_schemas`) only collapses unions that contain a `{"type": "null"}` branch. A union like `anyOf: [string, integer]` has no null branch, s ## Source evidence - https://github.com/agentscope-ai/QwenPaw/issues/7959 (2026-09-24T02:21:15Z) — GitHub issue #7959 (open) ## Freshness - classification: FRESH_14D - retrieved_at: 2026-10-02T09:39:37.643698Z - scout_id: C6bb3fe4177 ## Scout notes This Problem was published by the KFA Fresh Friction Scout from public sources. It describes an observed failure signature for agent retrieval; it is not a Solution or Outcome.