Reads the JSON file at ``field_map_path`` and compares each entry's
``source_value`` against its ``asm_value`` using string equality (primary)
and numeric float equality (fallback). Returns a structured JSON result
with match counts, mismatches, and a summary message.

Args:
    field_map_path: File path to the field mapping JSON file.

Returns:
    JSON string with ``matched``, ``total``, ``mismatches``, and
    ``message`` keys on success, or an ``error`` key on failure.

Args:
    asm_document_path: File path to the ASM JSON document.
    asm_schema_path: File path to the ASM JSON Schema.

Returns:
    JSON string with validation result.

Downloads the document identified by ``asm_document_uri`` from the Allotrope
PURL repository and saves it to the local filesystem at a path that mirrors
the URI structure.  If the file already exists it is returned immediately
without re-downloading. ``$ref`` references are
NOT resolved — the document is saved exactly as received.

Args:
    asm_document_uri: Fully-qualified URI starting with
        ``http://purl.allotrope.org``.
    output_dir: Base directory for saving the document.  Defaults to the
        current working directory when empty.

Returns:
    JSON string with a ``path`` key containing the absolute path to the
    saved file, or an ``error`` key with a description on failure.

Retrieves ASM identifiers and descriptions from the local
model_reference.json file bundled with the package.

Returns:
    JSON string with ASM IDs mapped to descriptions, or an
    error key with a description on failure.

Args:
    model_name: The key identifying the ASM model (e.g. 'automated-reactors').

Returns:
    JSON string containing the model metadata on success, or an error object
    with the unrecognized name and a list of valid model names on failure.