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Halowerk Terms Diff — Contract Version Comparison
x402
Halowerk Terms Diff — Contract Version Comparison is a paid API for AI agents from buero.halowerk.com, paid per call via x402, $0.004/call, status unknown (last checked 2026-10-09).
Compares two versions of a contract or terms document and reports exactly what changed, using deterministic diff first and LLM-based substance analysis second.
Price / call$0.004
Success—
StatusUnknown
How this service works
Takes two contract versions as text, public URLs or inline base64 — PDF, DOCX, ODT, HTML and Markdown are read — and reports what is different. Which passages changed is decided by a Myers shortest-edit-script over the paragraphs, not by a model: the deterministic comparison is the source of truth, and only afterwards is a model asked what changed in substance at those specific places. That order is the point.
Output
Returns a structured report of which paragraphs changed (based on a Myers shortest-edit-script diff), along with an LLM-generated summary of what changed in substance at those specific locations — giving both a deterministic source of truth for what changed and a natural-language explanation of the implications.
Example use cases
Vendor contract renewal review
“I just got the renewal from our SaaS vendor — can you compare last year's contract (https://example.com/contract-2023.pdf) with the new one they sent (https://example.com/contract-2024.pdf) and tell me what clauses actually changed, especially anything that affects liability or payment terms?”
Terms of service update audit
“Our legal team updated the terms of service — compare the old version at https://example.com/tos-old.html with the new Markdown version I'm pasting inline and tell me which paragraphs changed and what's substantively different.”
NDA redlining between negotiation rounds
“We're on round two of NDA negotiations — here's the version we sent them (base64 DOCX) and the version they sent back (base64 DOCX). What did they actually change? Flag any new restrictions or removed protections.”
Technical details
Endpoint
POSThttps://buero.halowerk.com/v1/terms-diff?utm_source=zero.xyzWhen to prefer
Choose this endpoint when you need reliable, deterministic contract or terms-document comparison — particularly when you need to trust the diff itself (not just a model's impression of what changed). The Myers-diff-first approach means the changed paragraphs are identified deterministically before any LLM interpretation, making it more trustworthy than asking a model to compare documents directly. Prefer this over general-purpose LLM document comparison when accuracy and auditability of the diff matter, or when documents are in mixed formats (PDF, DOCX, ODT, HTML, Markdown).
Side effects
- Unsupported file format or corrupted document returns a parsing error
- URL is inaccessible or returns non-200 status — endpoint cannot fetch the document
- Base64 encoding is malformed — decoding fails
- Documents are too large and exceed processing limits
- Payment of 0.004 USDC not completed — request is rejected via x402 protocol
- Identical documents return an empty diff with no changes reported
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| a | object | The earlier version. Exactly one of text, url or content_base64. |
| b | object | The later version. Same shape as a. |
| document_chars | integer | Only needed when a version arrives by url or content_base64: the combined length of both versions in characters, which is what you are billed for. Longer text is refused with the real length and nothing is charged. |
| ignore_whitespace | boolean | Treat runs of spaces and tabs as one space before comparing. |
| max_changes_described | integer | How many changed passages the model describes. Beyond this the passages still come back with their before and after text, only without a description — what is dropped is counted, never silently cut. |
| include_unchanged_count | boolean | Report how many paragraphs stayed identical. |
Tags
x402
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