Short answer

HubSpot's developer docs: CONTAINS_TOKEN accepts * wildcards for partial matches. A free-text query searches each object's default searchable properties, which for companies include name, domain, website and phone. Queries max out at 3,000 characters and any query returns at most 10,000 results.

1. The request

POST /crm/v3/objects/companies/search
{ "filterGroups": [ { "filters": [
  { "propertyName": "name", "operator": "CONTAINS_TOKEN", "value": "acme*" } ] } ] }