A market-data API is a programmatic interface for requesting or receiving a specified information product. The interface, the information coverage and the permission to use that information are separate parts of access.

Coverage determines the question a feed answers

A consolidated quote combines information across its defined market coverage. A direct exchange feed describes the products and events offered by that exchange. Depth, trades, auctions and market-status messages are different content categories, even when they travel through similar client software.

The Consolidated Tape Association aggregates trade and quote information for its covered US equity networks and calculates a national best bid and offer, or NBBO. NYSE direct products include order-book depth and auction information. A consolidated best quote does not contain every venue’s complete order book.

Take one consolidated best quote and a direct feed showing five price levels on one venue. The consolidated quote answers a question about the best prices across its covered market. The direct feed answers a deeper question about the book at that venue. More depth and broader venue coverage are different properties.

Transport preserves the product’s meaning

A feed handler receives messages, tracks sequence, handles recovery and maps identifiers. A gap in a sequence changes what the application knows about the current book. Reconnecting a socket does not establish that the missing events have been recovered.

A snapshot reports a state at a defined time. An event feed reports changes from which an application constructs state. Their consumers need different update and recovery rules. Comparing transport delay without identifying the update semantics leaves the measurement incomplete.

Timestamps also need an identified meaning. An exchange event time and the time a client received that event answer different timing questions. Labeling both as a single price timestamp erases that distinction.

Software access and information rights

A software development kit, or SDK, supplies client software. Installing it does not grant the data entitlements required by the requested service. Bloomberg’s Server API documentation checked in September 2026 requires an active Bloomberg Professional session for delivery to the user. The publicly accessible SEC data APIs provide a different information service and access arrangement.

Display, calculation, automated use, redistribution and storage are distinct use cases whose permissions depend on the applicable agreement. Technical access to a price does not specify every permitted downstream use.

The complete access description therefore names the interface, information product, market coverage, update semantics, recovery behavior and authorized use. An API label alone leaves most of that description open.

Questions about SIP

Does a free SDK include market data?

No. Client software and data entitlement are separate grants.

Is an exchange feed a complete view of the market?

No. An exchange feed describes its specified venue and product coverage.