Core concepts
Five ideas cover almost everything you’ll do with the API.
Models
Section titled “Models”A model is a document type plus the schema you want back (the same thing the app
UI calls a parser). You parse against a model id. Prefer to skip schema
design? Use schemaless extraction (POST /v1/extract) and LangParse infers
the fields for you.
Async by design
Section titled “Async by design”Parsing returns a documentId immediately (HTTP 202). Poll the document until
status is processed — no long-held connections. The status moves through
queued → processing → processed (or failed).
Fields & confidence
Section titled “Fields & confidence”Each extracted field comes back with a confidence of high, medium, low,
or flagged, plus bounding boxes — so you can auto-accept high-confidence
values or route the rest to human review. This is how you measure accuracy
rather than assume it.
Routers
Section titled “Routers”Classify an incoming file and split multi-document PDFs, then send each part to the right model automatically — so a mixed upload becomes cleanly separated, correctly-typed results.
Keys & scopes
Section titled “Keys & scopes”API keys carry scopes:
parse— submit documents and read results (new keys are parse-only).manage— configure models, routers, and sources.admin— organization administration.
Use a separate key per environment so usage is attributable and revocation is surgical.