Kimi Code API Invalid Moonshot flavoured json schema

[petterssonjonas]

Description

The Kimi Code plans now have API access, instead of just oAuth.

When sending a prompt i get:

tools.function.parameters is not a valid moonshot flavored json schema, details: <At path 'root': when using anyOf, type should be defined in anyOf items instead of the parent schema>

when using openai endpoint.

When using the anthropic endpoint i get:

Not Found: {"error":{"message":"The requested resource was not found","type":"resource_not_found_error"}}

FYI the models are now called 'k3' and 'kimi-for-coding' (k2.7) using the API.

Related issues:

There are no other issues referencing this specific issue when using the Kimi Coding plan API.

• Issue 25495 appears to bring up the same issue, but with the Moonshot API. This issue has a PR related to it, tough it may not fix the json flavour issue: 31580
• Issue 31580 appears related but produces a different error, and does so targeting the Opencode Go API.
• Issue 27054 appears to target the same problem but with the Moonshot API.

[edit]

Further testing

I have now tested this without oh-my-openagent / OmO, and the issue still occurs.

Test configuration

I removed OmO and tested with plain OpenCode tools only. No OmO-specific agents or delegation tools were active.

I tested both supported Kimi Code API protocols:

1. OpenAI-compatible endpoint
2. Anthropic-compatible endpoint

Both endpoints successfully reach the Kimi API, but both are rejected with the same schema-validation error:

tools.function.parameters is not a valid moonshot flavored json schema, details: <At path 'root': when using anyOf, type should be defined in anyOf items instead of the parent schema>

Result

The error is reproducible:

• With OmO enabled
• With OmO disabled
• Through the OpenAI-compatible endpoint
• Through the Anthropic-compatible endpoint

This indicates that the problem is not caused by:

• OmO tool definitions
• OmO agents or delegation tools
• Selecting the wrong API protocol
• An incorrect endpoint path

At least one tool schema generated by OpenCode itself appears to contain a structure equivalent to:

{
  "type": "object",
  "anyOf": [
    {
      "properties": {}
    },
    {
      "properties": {}
    }
  ]
}

Moonshot's validator appears to require the parent type to be moved into each anyOf item:

{
  "anyOf": [
    {
      "type": "object",
      "properties": {}
    },
    {
      "type": "object",
      "properties": {}
    }
  ]
}

This is valid standard JSON Schema but is not accepted by Moonshot's restricted schema implementation.

Likely required fix

OpenCode likely needs a Moonshot/Kimi-specific tool-schema normalization step before sending tool definitions.

For schemas containing anyOf and a parent-level type, OpenCode should remove the parent-level type and add it to each anyOf branch that does not already define its own type.

Conceptually:

if (Array.isArray(schema.anyOf) && schema.type) {
  const parentType = schema.type
  delete schema.type

  schema.anyOf = schema.anyOf.map((item) => ({
    type: item.type ?? parentType,
    ...item,
  }))
}

The transformation should be recursive because the same pattern may occur inside nested properties, array items, or referenced definitions.

This appears to belong in the same provider-specific schema-sanitization layer needed for other known Moonshot restrictions, including:

• $ref expansion conflicts
• if / then / else
• schema nesting-depth limits
• conflicting sibling keywords after $ref expansion
• parent-level type combined with anyOf or potentially oneOf

Conclusion

Kimi Code API access currently appears unusable with standard OpenCode tool calling, even without plugins.

A minimal plain OpenCode session still sends at least one built-in tool schema that the Kimi/Moonshot validator rejects. Switching between the OpenAI-compatible and Anthropic-compatible Kimi endpoints does not avoid the issue because both appear to use the same Moonshot-flavoured JSON Schema validation.

[/edit]

Plugins

OmO

OpenCode version

1.18.3

Steps to reproduce

Add kimi code provider using the api
send a prompt

Screenshot and/or share link

No response

Operating System

Fedora

Terminal

Ghostty