openai-tool-schema-strict

name	openai-tool-schema-strict
description	Enforce strict OpenAI function tool JSON schema rules when defining tool parameters
compatibility	opencode
metadata	{"audience":"ai-agents","scope":"tool-schema"}

What I do

• Ensure every tool schema uses parameters with type: object, properties, required, and additionalProperties: false.
• Enforce OpenAI strict rule: required must include every key declared in properties, even nullable ones.
• Keep optional behavior via nullable types (for example "type": ["string", "null"]), not by omitting from required.
• Prevent common 400 errors like invalid_function_parameters and Missing '<field>'.

Rules to apply

• For each property in parameters.properties, add the same key to parameters.required.
• If a field is logically optional, make it nullable and handle null in runtime validation.
• Always set additionalProperties: false unless there is an explicit requirement to allow arbitrary keys.
• Keep schema and handler aligned: if schema allows null, runtime coercion must accept None.

Quick checklist before finishing

• Compare set(properties.keys()) with set(required); they must match exactly.
• Verify no extra names appear in required.
• Verify each tool has consistent defaults/coercion for nullable inputs.
• Run lint/tests relevant to tool files.

Minimal pattern

{
  "type": "object",
  "properties": {
    "input": { "type": "string" },
    "limit": { "type": ["integer", "null"], "minimum": 1 }
  },
  "required": ["input", "limit"],
  "additionalProperties": false
}

Anti-pattern

{
  "type": "object",
  "properties": {
    "input": { "type": "string" },
    "limit": { "type": ["integer", "null"] }
  },
  "required": ["input"]
}