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API ReferenceOptions Flow

Status

Borrow fee & availability

GET/api/v3/short/borrow/{ticker}
Plan
Pro and up
Price
4 credits per call
MCP tool
short_borrow

Daily borrow cost and availability for a US stock from a broker-lending feed: indicative borrow fee and rebate (percent per year) and shares available to borrow, one row per trading day (that day's last snapshot). Availability is reported only up to 10,000,000 shares; above that shares_available is null and shares_available_min is 10,000,000. History from 2026-03-16, updated each trading day. This is borrow supply, not short interest; FINRA's settled short interest in the window is listed for context. Use for hard-to-borrow and squeeze-cost checks. Window up to 366 days.

Parameters

Path

tickerstringRequired

Query

startstringOptional

YYYY-MM-DD; default end minus 90 days.

endstringOptional

YYYY-MM-DD; default today.

limitintegerOptional
Default120
Range1 to 400

Response

A 200 is a JSON envelope: ok: true and this endpoint's own fields (see Options Flow). It carries X-Request-ID, the credit headers (X-Credits-Cost, X-Credits-Remaining, X-Credits-Receipt, X-Credits-Settlement) and the rate-limit headers.

A 200 is billed even when it holds no data (an empty list, null, found: false), so check those fields. Pricing & credits explains the credit headers.

Errors

No error is billed. The body is { "ok": false, "error", "detail", "request_id" }; read the code from error.

ErrorMeaning
400 invalid_tickerThe request is malformed, for example a ticker that is not a symbol: invalid_ticker, refused before any credit is reserved, with param naming the parameter. Not billed.
401 unauthorizedMissing or invalid API key.
402 plan_requiredYour plan does not include this tool, you are out of credits, or your workspace's spend cap paused its keys. plan_required names the plan that unlocks the tool; usage_exceeded means the credit balance is spent; spend_cap_reached means the key is paused until the cap resets or is raised: detail names the cap and the reset, cap_usd and resets_at (ISO 8601) carry them, and doc_url links pricing and credits. Not billed.
403 scope_deniedThis API key is limited to some products and this tool is not one of them. product names the tool's product and scopes the key's products. An upgrade does not change it: use a key whose scopes include the product, or change this key's scopes. Not billed.
404 unknown_tickerNo data source lists this ticker, active or delisted: the market-data listing and the security master both say it does not exist. param names the parameter. Not billed. Best-effort: it is answered only when the route itself found nothing, and after 20 lookups of new symbols per API key per minute the route's own answer stands.
422 validationA parameter is missing, out of range or the wrong type; param names it. Not billed.
429 rate_limitedYour plan's rate limit is spent for this window. Retry after Retry-After seconds. Not billed.
503 paid_data_unavailableThe data could not be served completely right now; retry later. Not billed.
504 request_timeoutThe request ran past the server's time budget; retry. Not billed.

This table lists what the spec declares for this route. Error responses lists every code FIRM sends, with when to retry.

Guides

Read the Options Flow guide for this endpoint's fields and examples.