# LLM Catalog Diff

> LLM Catalog Diff is a paid API for AI agents from modell.halowerk.com, paid per call via x402, $0.005/call, status unknown (last checked 2026-10-28).

Computes a deterministic field-level diff between two LLM catalog snapshots, identifying added, removed, and changed models with per-field pricing and capability deltas.

## Facts

- Endpoint: POST https://modell.halowerk.com/v1/llm-catalog-diff?utm_source=zero.xyz
- Price: $0.005/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-28
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/llm-catalog-diff-452f80a9
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_KxUQZ8tyVv1j-rRr8MTUU

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 llm-catalog-diff-452f80a9 -d '<json body>'
```

Example prompt: I have last month's LLM catalog and today's updated one — can you diff them and tell me which models were added or removed, and exactly which pricing or context window fields changed for any existing models?

## When to prefer this

Use this endpoint when you need a deterministic, structured diff between two snapshots of an LLM catalog — especially before changing routing logic, updating budgets, or auditing for deprecated or newly added models. Prefer this over manually comparing catalog arrays when you need field-level granularity on pricing and capability changes across up to 500 models per snapshot. This is the right choice when traceability and reproducibility of catalog changes matter for downstream automation.

## Known failure modes

- Missing required model identifier (model, id, or name) in any catalog entry returns a validation error
- Empty array or array exceeding 500 items returns a schema validation error
- Ambiguous model matching when vendor is omitted and model names collide across providers may cause unexpected diffs
- Null values for pricing fields are treated as unknown and may produce misleading change reports if one snapshot has nulls and the other has values
- Network timeout or payment failure returns a 402 or 5xx error

## How this service works

Use this when an agent has an older and a newer LLM catalog snapshot and needs a deterministic migration diff before changing routing or budgets. Rows are matched by vendor plus model, id or name. The result separates added, removed and changed models and reports field-level differences for input, output and cached-input price, context window and maximum output tokens.

## Output

Returns a structured diff object with three sections: 'added' (models in the after snapshot but not before), 'removed' (models in the before snapshot but not after), and 'changed' (models present in both with field-level differences for input_price_per_million, output_price_per_million, cached_input_price_per_million, context_window, and max_output_tokens, showing before and after values for each changed field).

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method",
    "bodyType"
   ],
   "properties": {
    "type": {
     "const": "http"
    },
    "method": {
     "const": "POST"
    },
    "bodyType": {
     "const": "json"
    },
    "schemaUrl": {
     "type": "string",
     "format": "uri"
    },
    "exampleUrl": {
     "type": "string",
     "format": "uri"
    }
   },
   "additionalProperties": true
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "const": "json"
    },
    "schemaUrl": {
     "type": "string",
     "format": "uri"
    },
    "exampleUrl": {
     "type": "string",
     "format": "uri"
    }
   },
   "additionalProperties": true
  }
 },
 "additionalProperties": true
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/llm-catalog-diff-452f80a9/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)