sellsy.

In Sellsy: Settings → Developer portal → API V2 → create an access. Choose a personal access ("personal"): it is the one that issues a token directly from the id/secret pair, without going through a browser.

Then paste into oto:

Tick the rights (scopes) matching what the agent will need to do: read-only to look things up, write to create third parties or documents. A missing right shows up as an HTTP 403 refusal at call time, not at connection time.

byo only: a Sellsy account belongs to a company, there is no key shared by oto. The access inherits the permissions of the staff member it is attached to.

Sellsy holds both ends: who the clients are, and what they are invoiced.

Identifiers (pipeline step, tax, staff member, custom field) are read with sellsy_ref — never guess them.

Two reflexes are worth knowing before letting the agent write.

Dry run. op="create" accepts dry_run=true: Sellsy validates the body and persists nothing. Useful before a serial creation, since required fields vary from one account to another (numbering, custom fields).

Validating is irreversible. A created document is a draft; op="validate" on an invoice or a credit note freezes its number and makes it accounting-relevant. Reserve it for a human decision. A quote, by contrast, simply changes state (op="status").

Sellsy quotas are counted per second, minute, day and month, and every request counts, even in error: prefer filters + fields over a wide all_pages.

this connector accepts multiple comptes: each stored credential becomes a named account (one name per compte), at your level, your team's or your org's.