Sandbox environment
A sandbox environment is a separate instance of an API where developers can make real calls against test data without touching production systems or incurring live charges. Sandboxes typically use a distinct base URL and test credentials, and often provide simulated behaviors — test card numbers, mock events, forced error states — for exercising flows that would be costly or irreversible in production.
Agents verify their own work by executing it. A coding agent scaffolding an integration wants to run the calls it just wrote, and a documented sandbox is the only place that loop is safe — production is where an agent's exploratory POST becomes a real charge or a real email to a customer.
The documentation requirements are concrete: the sandbox base URL, how test credentials are issued, exactly how sandbox behavior diverges from production, and the fixtures available for simulating edge cases. An agent that can read 'use 4242 4242 4242 4242 to simulate a successful card' can test a payment flow end to end; one that cannot find the divergences will draw wrong conclusions from sandbox quirks.
The most common failure is ambiguity between environments. Docs that interleave sandbox and production URLs without clear labeling invite an agent to mix them — test credentials against production endpoints, or the reverse — and the resulting errors point nowhere near the actual cause.
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