Access Tier

Access Tier is AAMP’s four-value string enum for what a buyer agent is allowed to see and pay. On the wire it is buyer_tier, carried on the Quote, Deal and Negotiation objects and glossed “Access tier for tiered pricing, derived from revealed buyer identity”.

All three objects declare it identically: {"$ref": "#/$defs/AccessTier", "default": "public"}. A buyer that sends no identity is priced at the public tier rather than rejected.

The schema derives the tier from revealed buyer identity. In the reference implementations the seller’s API key fixes it instead, and an identity sent in the payload can only confirm what the key already allows.

The repository that defines it is unreleased and warns that its schemas will change without notice. There is no canonical AccessTier.json: the same block is copied into five schema files, and the two reference agents no longer derive the tier the same way.

Entitlements at each tier

Pricing visibility, negotiation and availability detail all move together. The discounts below are the reference seller agent’s _default_tiers() fallback, which an operator overrides, rather than a published rate.

The reference seller agent also maps the effective tier to a named negotiation strategy, with three hard limits and one behavioural parameter. These are that agent’s defaults, not protocol.

Buyer gap share, gap_split_buyer_share on the wire, rises with the tier: at advertiser the seller expects the buyer to close 65 percent of the remaining gap, alongside the widest concession budget. docs/integration/negotiation.md glosses the field as “How much of the price gap the seller expects the buyer to close (higher = more favorable to seller)”. The worked example is on AAMP Explorer; the round record is a Negotiation Round.

The tier also controls how much availability detail a caller sees, which the tier documentation does not cover. A public caller is told a product is Available, a seat caller that availability is High, and agency and advertiser callers get numbers: estimated_monthly_impressions of 10M-50M, a fill_rate of 85-95%.

The default rate card sets negotiation_enabled=False for public and seat, and the seller’s negotiation engine never reads the flag.

What sets the tier

BuyerIdentity has eleven properties and no required array, so an empty BuyerIdentity {} validates. Only seat_id, agency_id and advertiser_id change the tier; neither reference implementation branches on dsp_platform, advertiser_name or the campaign fields.

A brand buying direct, with no agency and no seat, computes advertiser on its own agent while the seller walks the same identity down to ANONYMOUS and quotes a range. Neither agent raises an error, and the buyer is quoted at the lower tier. The two agents disagree about how many IDs the top tier needs: the seller requires both an advertiser ID and an agency ID, and its identity_level reaches AGENCY_AND_ADVERTISER only when both are present, while the buyer treats an advertiser ID alone as enough. The buyer’s model carries the seller’s rule as a comment, # Agency + Advertiser - 15% discount, and does not implement it.

The revelation mechanism the buyer’s documentation describes is not wired up. to_header_dict() builds X-DSP-Seat-ID, X-Agency-ID and X-Advertiser-ID, no code in the repository calls it, and the seller reads only Authorization and X-Api-Key. docs/api/authentication.md states the arithmetic: “The effective tier is the minimum of the API key tier and the agent trust tier. A preferred agent with a seat-level API key gets seat access.” A BuyerIdentity sent afterwards cannot raise the tier above what the key allows. The ceiling side of that minimum is Trust Status.

The schema states that the tier is “capped server-side by the registry-verified trust status of the calling agent — it is never self-asserted”, over the order public < seat < agency < advertiser. Quotes, deals and negotiation all go through _verified_buyer_context, which floors the effective tier to public when the claim is unverifiable.

One discovery endpoint in the reference seller agent does not apply that cap. POST /media-kit/search bypasses _verified_buyer_context, builds a buyer context whenever api_key_record is not None or request.buyer_tier != "public", and leaves max_access_tier unset, so an unauthenticated caller claiming advertiser is answered at that tier: exact_price at the top-tier discount, floor_price, placements, audience segment IDs and negotiation_enabled: true. It is a defect in that repository rather than a reading of the schema.

Access tier in AdCP

AdCP 3.1.13 defines no access tier, and no tier, access_tier, buyer_tier or account_tier property in dist/schemas/3.1.13/. The relationship is modelled under another name: core/account.json describes “the relationship between a buyer and seller”, an account that “determines rate cards, payment terms, and billing entity”, and its rate_card is {"type": "string"}, so the rate card is named and its contents are left to the parties. Capability lives in core/account-authorization.json, an allowlist of task names in allowed_tasks[] plus field_scopes and read_only.

AdCP’s account_scope is also a four-value enum on the buyer relationship — operator, brand, operator_brand, agent — but its values are categories, not levels, so they do not compose into a ceiling. The rest of that shape difference is in the protocol comparison.