# Tool Argument Validator

> Tool Argument Validator is a paid API for AI agents from modell.halowerk.com, paid per call via x402, $0.002/call, status unknown (last checked 2026-09-13).

Validates tool call arguments against a JSON Schema and flags semantic anomalies like placeholder values, suspicious numbers, destructive flags, and checksum failures.

## Facts

- Endpoint: POST https://modell.halowerk.com/v1/tool-arg-validate
- Price: $0.002/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-13
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/tool-argument-validator-34f104b3
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_tiU69ie_jQKZBZ9L8Vfev

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability tool-argument-validator-34f104b3 -d '<json body>'
```

Example prompt: Before you call that tool, check these arguments against the tool's input schema — flag any schema violations and also catch anything that looks semantically wrong, like a placeholder 'string', a TODO, an empty field that should have content, or a destructive flag set to true.

## When to prefer this

Use this endpoint when you need both structural schema validation AND semantic sanity checking of tool arguments in a single call — especially in agentic pipelines where LLMs may fill required fields with placeholder text or set dangerous flags inadvertently. Prefer it over pure JSON Schema validators when you care about catching 'technically valid but obviously wrong' values before a tool is invoked.

## Known failure modes

- Missing or malformed tool input schema returns a schema-parse error
- Arguments payload that is not valid JSON returns a parse error
- Ambiguous schema definitions (e.g. oneOf without discriminator) may reduce anomaly detection accuracy
- Checksum-style checks are heuristic and may produce false positives for non-standard address formats
- Numeric order-of-magnitude checks depend on field naming heuristics and may miss domain-specific ranges

## How this service works

Two checks in one. First the arguments are validated against the tool input schema and every violation is reported with its path and a sentence saying what to change. Second, values that satisfy the schema but look wrong are flagged: an unset required field filled with a placeholder like "string" or "TODO", a number at a suspicious order of magnitude, an address that fails its checksum shape, a destructive flag set to true, an empty string where content was expected.

## Output

A structured report listing: (1) schema violations with JSON path, the broken rule, and a plain-English fix suggestion; (2) semantic anomalies such as unfilled placeholder strings ('string', 'TODO'), numbers at a suspicious order of magnitude, addresses failing checksum shape, destructive flags set to true, and empty strings where content was expected — each with its field path and a description of what looks wrong.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "schema": {
   "type": "object",
   "description": "The tool input schema."
  },
  "arguments": {
   "type": "object",
   "description": "The arguments about to be sent."
  },
  "tool_name": {
   "type": "string",
   "maxLength": 128,
   "description": "Name of the tool, carried into the report."
  },
  "irreversible": {
   "type": "boolean",
   "default": false,
   "description": "Mark the call as irreversible. Raises every warning one level."
  },
  "expected_magnitude": {
   "type": "object",
   "description": "Optional per-field order-of-magnitude hint, e.g. {\"amount\": 100}. A value more than 100x off is flagged.",
   "additionalProperties": {
    "type": "number"
   }
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/tool-argument-validator-34f104b3/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from modell.halowerk.com](https://www.zero.xyz/host/modell.halowerk.com/llms.txt)