Moss - Real-time Semantic Search for Conversational AI

create_index_from_files builds a new index directly from raw documents. You upload PDF and DOCX files; the server parses them, splits them into chunks, generates embeddings, and builds the index. The call returns when the index is ready to query.

Requires moss 1.7.3+. Also available in JavaScript as createIndexFromFiles (@moss-js/moss 1.8.0+). chunk_size and chunk_overlap need 1.17.0+ (JavaScript 1.18.0+).

from moss import MossClient, ParseFileInput, ParseOptions

client = MossClient(MOSS_PROJECT_ID, MOSS_PROJECT_KEY)

await client.create_index_from_files("contracts", [
    ParseFileInput(name="report.pdf", content_type="application/pdf", path="/docs/report.pdf"),
    ParseFileInput(
        name="manual.docx",
        content_type="application/vnd.openxmlformats-officedocument.wordprocessingml.document",
        data=docx_bytes,  # raw bytes also work
    ),
], parse_options=ParseOptions(ocr_mode="full_ocr"))  # scanned documents with no text layer

# Query the new index server-side right away - no load_index needed
results = await client.query("contracts", "termination clause")

How it works

The call handles the full flow: it registers the files, uploads each one, and triggers parsing, embedding, and the index build server-side. It blocks until the index is ready and returns a MutationResult. Jobs time out after 30 minutes. There is no progress callback in Python.

Files

Each entry is a ParseFileInput:

Field	Required	Notes
`name`	Yes	Identifier for the file. Names must be unique within the call - uploads are matched back to files by name.
`content_type`	Yes	`application/pdf` or `application/vnd.openxmlformats-officedocument.wordprocessingml.document` (DOCX). Not inferred from the file name; any other value is rejected before upload.
`path`	One of `path` / `data`	Filesystem path.
`data`	One of `path` / `data`	Raw file bytes (`bytes`). Takes precedence over `path` when both are set.

Limits:

1 to 20 files per call. Each call creates a new index, and files cannot be appended to an existing index afterwards, so an index is built from at most 20 files.
50 MB per file, enforced server-side. The SDK does not pre-check size; an oversized file fails during the job.

Options

model_id (Optional[str] = None) - defaults to "moss-minilm"; "moss-mediumlm" is also supported. "custom" is not supported - the server generates embeddings during parsing.
parse_options (Optional[ParseOptions] = None) - extraction controls, below.

Parse options

All fields of ParseOptions are optional; omitted fields use the server defaults.

Option	Values	What it does
`ocr_mode`	`"auto_ocr"` \| `"full_ocr"`	`full_ocr` forces OCR on every page, which is what scanned documents with no text layer need. `auto_ocr` runs OCR only where it looks necessary.
`use_high_resolution`	bool	Slower, higher-fidelity extraction. Useful for dense tables.
`segmentation_method`	`"smart_layout_detection"` \| `"page_by_page"`	How the document is segmented before extraction.
`merge_tables`	bool	Merge a table split across a page break into a single segment.
`chunk_size`	int (characters)	Maximum chunk length, 200-2000; default `1200`. Chunks end at `.`, `!` or `?` before a capital letter; a longer sentence is cut at spaces, or mid-word if it has none. The title prefix is not counted. (moss 1.17.0+)
`chunk_overlap`	int (characters)	Characters repeated from the end of one chunk at the start of the next, 0 to half of `chunk_size`; default `200`, or half of `chunk_size` when smaller. The overlap moves forward to a sentence start when one falls inside it, and is absent around long sentences. (moss 1.17.0+)

The extraction options shape the text the parser extracts; chunking then runs over it as one stream per file.

What gets indexed

Documents are split into chunks of up to chunk_size characters overlapping by up to chunk_overlap, each prefixed with a title (the document’s title or first heading, else the file name) that is part of the hit text returned by query. Repeating page headers, footers, page numbers, and images are excluded from the indexed text. A scanned or image-only document produces no readable text unless OCR runs - if a file fails with “No readable text was found”, retry with parse_options=ParseOptions(ocr_mode="full_ocr").

Querying a parse-built index

Query the index without loading it - client.query(name, text) runs server-side when the index is not loaded locally:

from moss import QueryOptions

results = await client.query("contracts", "termination clause", QueryOptions(top_k=5))

Local text queries are not yet supported for parse-built indexes: after load_index(), a plain text query() raises an error. Either query without loading the index, or pass your own query embedding via QueryOptions.embedding.

Errors

Passing model_id="custom" raises ValueError before anything is uploaded. Other failures raise MossError; str(e) is fixed text, e.detail starts with:

`detail` starts with	Cause
`Validation error: files must not exceed 20`	More than 20 files in one call.
`Unsupported content type`	`content_type` is not PDF or DOCX.
`Validation error: Unsupported chunk_size`	`chunk_size` outside 200-2000. Rejected before upload, not clamped.
`Validation error: Unsupported chunk_overlap`	`chunk_overlap` negative or above half of `chunk_size` (600 when `chunk_size` is omitted).
`Model not allowed:`	The model is not enabled for your organization.
`Upload failed:`	A file could not be read or uploaded.
`Job failed:`	Parsing or the index build failed server-side.
`Job timed out after 1800 seconds`	The job exceeded the 30 minute polling ceiling.

Python

JavaScript

Swift (iOS)

Android

Elixir

Browser

C

Index from Files

How it works

Files

Options

Parse options

What gets indexed

Querying a parse-built index

Errors

​How it works

​Files

​Options

​Parse options

​What gets indexed

​Querying a parse-built index

​Errors

How it works

Files

Options

Parse options

What gets indexed

Querying a parse-built index

Errors