Brex and Tally twins

Your agent can now issue cards and pay vendors on Brex, or build a Tally form and read the responses, without touching a real account. Add either twin to an environment and point your HTTP client at the hostname it gives you.

Brex twin

The Brex twin covers seven of Brex's APIs: Team, Transactions, Payments, Expenses, Budgets, Fields and Accounting. Your agent can issue, lock and terminate cards, set spend limits under a budget, pay vendors through approval, and attach receipts to expenses. Each environment starts with one company, its account admin, a root budget, a card account and a cash account.

The twin holds agents to Brex's rules. Card creation, transfers and budget writes need an Idempotency-Key. Tokens carry scopes, and the cards scope won't show a full card number; your agent needs cards.pan for that. When you advance the environment, transfers move toward processed, shipped cards activate, and budgets and spend limits roll into their next period.

Brex has no official client library, so we check the twin's responses against the OpenAPI documents Brex publishes. Titles, cost centers, legal entities, incoming transfers, linked accounts and partner OAuth return a not-modelled response, as do the Onboarding, Travel and Webhooks APIs. See the Brex twin docs for the full list.

Tally twin

The Tally twin speaks API version 2026-08-04. Your agent can create a form from blocks, read the questions Tally derives from them, and page through submissions with filters and date ranges. Workspaces, folders, webhooks and organization invites work too.

Tally's limit of 100 requests a minute applies here, so an agent that polls for new submissions too often gets the same 429 it would get from Tally. Advancing the environment closes forms past their close date. Each newly completed submission adds a FORM_RESPONSE event to every enabled webhook's event log, though the twin doesn't deliver webhooks yet.

Analytics, form templates, file uploads and payments return a not-modelled response. The Tally twin docs list the rest.

Startup credits

Startups can apply for $1,000 in credits, to spend over six months. You qualify if your company was incorporated in the last five years, has raised less than $2 million and has fewer than 50 people. Apply through the short form on the startups page and we'll reply within five business days. The Free plan needs no approval, so you can start building while you wait.

Improvements

• Pricing: On phones, the plan comparison shows one plan at a time. Pick the plan you want from the menu at the top of the table.
• Website: Every page on twinbay.ai now has a Markdown version. Add /.md to the path, as in /twins/stripe/.md. Tools that ask for text/markdown get the same Markdown at the regular URL.
• Website: AI agents can find our docs and OpenAPI spec through the standard API catalog at /.well-known/api-catalog.

Fixes

• Fixed long labels in the pricing comparison table running into the next column.