Bug: ReadMediaFile tool pages parameter uses tuple-style items which is rejected by strict JSON Schema validators

Description

Bug: ReadMediaFile tool pages parameter uses tuple-style items which is rejected by strict JSON Schema validators
Description
The built-in ReadMediaFile tool defines a pages parameter whose JSON Schema uses tuple-style items:

"pages": {
"items": [
{"type": "integer", "exclusiveMinimum": 0, "maximum": 9007199254740991},
{"type": "integer", "exclusiveMinimum": 0, "maximum": 9007199254740991}
]
}
This format is valid in JSON Schema draft-07/draft-2019-09 (tuple validation), but JSON Schema 2020-12 changed items to accept only a single schema object or boolean, removing tuple validation.

Some API providers (e.g., Xiaomi Token Plan / MiMo models) validate tool schemas against JSON Schema 2020-12 and reject this format:

prefill failed: Tool 45 function has invalid 'parameters' schema: [{'type': 'integer', 'exclusiveMinimum': 0, 'maximum': 9007199254740991}, {'type': 'integer', 'exclusiveMinimum': 0, 'maximum': 9007199254740991}] is not of type 'object', 'boolean'

Failed validating 'type' in metaschema['allOf'][1]['properties']['properties']['additionalProperties']['$dynamicRef']['allOf'][1]['properties']['items']['$dynamicRef']['allOf'][0]:
Steps to Reproduce
Configure opencode to use a provider with strict JSON Schema 2020-12 validation (e.g., Xiaomi Token Plan with MiMo model)
Start a session
The API call fails immediately with the schema validation error
Expected Behavior
The tool schema should use JSON Schema 2020-12 compatible format. For a tuple/array of two integers, the fix would be:

"pages": {
"type": "array",
"items": {"type": "integer", "exclusiveMinimum": 0, "maximum": 9007199254740991},
"minItems": 2,
"maxItems": 2
}
Or use prefixItems (2020-12 syntax):

"pages": {
"type": "array",
"prefixItems": [
{"type": "integer", "exclusiveMinimum": 0, "maximum": 9007199254740991},
{"type": "integer", "exclusiveMinimum": 0, "maximum": 9007199254740991}
],
"minItems": 2,
"maxItems": 2
}
Environment
opencode version: 1.18.7
OS: Windows_NT 10.0.26200 x64
Plugin: oh-my-openagent
Provider: xiaomi-token-plan-sgp / mimo-v2.5-pro
Additional Context
This affects any provider that strictly validates tool schemas against JSON Schema 2020-12. Providers with more lenient validation (e.g., DeepSeek, OpenAI) accept the tuple format without issue, which is why this bug may not have been widely reported.

issue-bug-report.md
issue-bug-report.pdf

Plugins

oh-my-openagent

OpenCode version

1.18.7

Steps to reproduce

1. Configure opencode with a provider that validates tool schemas strictly against JSON Schema 2020-12 (e.g.,
   xiaomi-token-plan-sgp with mimo-v2.5-pro model)
   2. Start a new session in opencode TUI
   3. The API call fails immediately before any user interaction with: prefill failed: Tool 45 function has invalid 'parameters' schema

Screenshot and/or share link

No response

Operating System

Windows 11 (Windows_NT 10.0.26200 x64)

Terminal

Windows Terminal