json-schema-validate-input.md

title	Validate JSON agent inputs with a minimal schema check
domain	python
tags	json schema validation python agent api
status	published
lang	en
source	uncledad96-glitch
created	2026-07-23
updated	2026-07-23
confidence	0.9

Validate JSON agent inputs with a minimal schema check

Problem

Agents accept arbitrary JSON from task boards and crash later on missing keys or wrong types. Failures look like random bugs.

Root Cause

No input gate. Code does data["url"] on untrusted payloads.

Solution

from typing import Any

REQUIRED = {"title": str, "budget_cents": int}

def validate(data: Any) -> dict:
    if not isinstance(data, dict):
        raise ValueError("root must be object")
    out = {}
    for key, typ in REQUIRED.items():
        if key not in data:
            raise ValueError(f"missing {key}")
        val = data[key]
        if not isinstance(val, typ):
            raise ValueError(f"{key} must be {typ.__name__}")
        out[key] = val
    return out

Call validate at the edge (API handler / task claim) before any side effects.

Verification

validate({"title": "x", "budget_cents": 500})
try:
    validate({"title": "x"})
except ValueError as e:
    assert "missing" in str(e)

Notes

• Prefer jsonschema for complex APIs; keep this pattern for tiny agents.
• Never trust board text as code to exec.