GunSpec

Compatibility

Fit is computed from mount interfaces, never from names. A firearm declares what it exposes at each position (muzzle thread, rails, optic cut, stock and grip interfaces, magazine well); an attachment declares what it requires; the engine matches the two, through a named adapter where one bridges them. A caliber, bore or minimum-barrel mismatch is never bridged and never inferred.

Every fit carries `source` and `confidence`, and they are the first two fields to read. source is the weakest evidence in the chain that produced the fit; confidence is capped by the weakest interface it went through. The values, strongest first:

  • curated: a person recorded this interface or this fit against the maker's page.
  • universal: the attachment requires nothing (a sling), so every firearm fits it.
  • inherited:parent: the interface came from the firearm's parent record.
  • inherited:platform: the interface came from a platform the firearm belongs to (an AK-100 default, a mil-spec AR-15 default).
  • inferred: the interface was derived by a script from the record's own fields, at 0.6 or below. Convention rows are the weakest inferred evidence and are labelled as such: where a firearm is tagged threaded or optics-ready but names no standard, the backfill applies industry convention (a thread by cartridge and country, an optic plate by the maker's system) at 0.5 to 0.6, with a convention: note on the interface row.

A retailer or an engineering consumer should treat `inferred`, and anything below a confidence they choose, as unverified. Pass min_confidence to hide fits computed through interfaces below that figure; nothing in a response presents an inferred or convention row as verified, and neither should a product page built on it. via[] names each interface the fit went through with its own source, so a fit can be audited hop by hop; GET /v1/firearms/{id}/interfaces lists every row with its source, confidence and inheritedFrom.

Browsing the catalog (/v1/attachments, /v1/attachments/{id}, /v1/interfaces) is open to any key. Everything that answers "does this go on that" is Studio, and a lower plan receives 403 SUBSCRIPTION_REQUIRED rather than an empty list, so never read an error as "nothing fits". fits= on the attachment list is the same computation wearing a query parameter and is gated the same way.

Auth RequiredExplorer+

List interface standards

The controlled vocabulary of mount interfaces: rails, muzzle threads, optic footprints, stock and grip mounts, handguard mounts, magazine wells, side mounts, sight dovetails, bipod studs, sling points, trigger pockets and charging handles. Ids are kind-prefixed and stable.

GET/v1/interfaces

Explorer+

  • stringheaderrequired

    Your API key. Authorization: Bearer <key> is accepted in its place.

  • string

    One kind only

    Max length
    40
    Example

application/json

  • InterfaceStandard[]

    The response payload.

  • string

    Kind-prefixed standard id, e.g. thread:1/2x28. URL-encode it when addressing /v1/interfaces/{id}/firearms.

  • string

    What sort of interface it is: thread, rail, mag, stock_mount, optic_plate.

  • string

    Display name, as the maker writes it.

  • string[]

    JSON array of alternative spellings of this standard id, as a string. Ids are never renamed; a new spelling becomes an alias.

  • string | null

    Free-text notes that do not belong in a specific field.

  • 400VALIDATION_ERRORValidation error
  • 401UNAUTHORIZEDAPI key required
  • 403FORBIDDENValid key, not permitted
  • 429RATE_LIMITEDRate limit exceeded
  • 500INTERNAL_ERRORUnexpected server error

Full rate limits

Minimum tier
Explorer+
Monthly quota
200/mo
Rate limit
10/min
Daily cap
50

Figures shown are for this endpoint's minimum tier. Higher tiers raise every limit.

Caching guide

This read answers conditional requests. Keep the ETag from a response and send it back as If-None-Match: an unchanged record returns 304 Not Modified with no body, which counts toward your per-minute rate limit but not your daily allowance.