Worked examples

Operation	Method and path	Price
get_catalog	`GET /api/v2/catalog`	$0.05
resolve_entities	`POST /api/v2/resolutions`	$0.05
get_entity	`GET /api/v2/entities/{entity_ref}`	$0.05
traverse_relationships	`GET /api/v2/entities/{entity_ref}/relationships`	$0.05
search_properties	`POST /api/v2/property-searches`	$0.05
get_property	`POST /api/v2/property-queries`	$0.05
get_evidence	`POST /api/v2/evidence-lookups`	$0.05

Typical flow: catalog to learn what is covered, resolve or search to obtain references, get_property or get_entity to read records, traverse to move between related entities, get_evidence to verify.

get_catalog

GET /api/v2/catalog · $0.05 per call Describes what the API covers before you query it.

Query parameter	Type	Notes
`facet`	required	`jurisdictions`, `authorities`, `coverage`, `dictionary`, `capabilities`, `sources`
`area_uid`	optional	Filters `jurisdictions` and `coverage` only
`subject_kind`	optional	`coverage`: domain key. `dictionary`: entity name
`record_family`	optional	`coverage`: property class. `dictionary`: data type
`field_key`	optional	`dictionary` only
`limit`, `cursor`	optional	Pagination

Using a filter on a facet that does not support it returns HTTP 422 unsupported_filter.

Facet	Returns
`jurisdictions`	Areas, with official name and Census, USPS and FIPS identifiers. Today: `area_us_dc`
`authorities`	Issuing agencies, for example `auth_us_dc_otr` (Office of Tax and Revenue) and `auth_dc_mar` (Master Address Repository)
`coverage`	Per area and domain: `availability_status`, `observed_record_count`, `generation_id`
`dictionary`	Field definitions: `field_key`, `title`, `definition`, `data_type`, `unit`, `definition_status`
`capabilities`	The seven operations and the controls each supports
`sources`	Every ingested official dataset with `release_id`, `sha256`, retrieval time, official landing and download URLs

curl "https://portal.quoindata.com/api/v2/catalog?facet=coverage&area_uid=area_us_dc&limit=5" \
  -H "Authorization: Bearer $QUOIN_API_KEY"

{
  "facet": "coverage",
  "items": [{
    "area_uid": "area_us_dc",
    "domain_key": "property_record",
    "property_class": "all",
    "generation_id": "10",
    "availability_status": "available",
    "availability_reason": null,
    "observed_record_count": 215744
  }]
}

Coverage status values: available, partial, gated, unavailable, stale, source_unavailable, retired, not_applicable. A missing record in an available domain means no matching record exists in the current publication, not that no public record exists anywhere.

resolve_entities

POST /api/v2/resolutions · $0.05 per call, regardless of item count Turns official identifiers or street addresses into entity references. Batch up to 50 claims per call. Request body

Field	Type	Notes
`items[]`	1–50	One claim each
`items[].client_id`	string, required	Your correlation id, echoed back
`items[].subject_kind`	required	`property`, `tax_account`, `parcel`, `address`, `unit`, `building`, `land_interest`
`items[].area_uid`	recommended	`area_us_dc`. Required for address resolution
`items[].identifiers[]`	optional	`{ namespace, raw_value, normalized_value? }`
`items[].address`	optional	`{ line, unit?, locality?, region?, postal_code? }`
`items[].include_retired_identifiers`	boolean, default false	Also match retired identifiers
`candidate_limit`	1–50, default 10	Candidates returned per claim

Identifier namespaces in the current publication:

Namespace	Meaning	Example
`dc_ssl`	D.C. square-suffix-lot, 8 characters with or without punctuation	`04842250`, `0484--2250`
`mar`	D.C. Master Address Repository id	`158900`
`entity_ref`	A reference you already hold	`qentity_0000181b67f859019efe1b488b88b1f0`

Response data.items[]

Field	Meaning
`outcome`	`resolved`, `ambiguous`, `not_found`, `address_found_no_parcel`, `retired_only`, `invalid_input`, `unavailable`
`candidates[]`	Entities that matched, each with `entity_ref`, `entity_kind`, `status`, `area_uid`, `canonical_identity`, `match_basis`, `precision`, `method`, and `property_ref` when supported
`address_resolution`	How the address was interpreted: `normalized_input`, `method`, `precision`, `parcel_count`, `address_count`
`truncated`	More candidates existed than `candidate_limit`

precision and method describe address-based matching only. For identifier matches (match_basis: "identifier") both are null; the match is by official identifier. For address matches, precision is exact when the address maps to exactly one record, contextual when the match came through a parent (for example a unit resolved through its building’s address), and ambiguous when several records fit. A contextual match is context, not proof of identity. Address handling: punctuation and whitespace are normalized; a missing D.C. quadrant (NW, NE, SW, SE) is tried in all four positions and reported as method: "dc_quadrant_fallback" with precision: "contextual"; a unit value is carried through and matched separately.

{
  "items": [
    { "client_id": "docs-ssl", "area_uid": "area_us_dc", "subject_kind": "tax_account",
      "identifiers": [{ "namespace": "dc_ssl", "raw_value": "04842250" }] },
    { "client_id": "docs-address", "area_uid": "area_us_dc", "subject_kind": "property",
      "address": { "line": "1477 Newton St NW", "unit": "402" } }
  ]
}

{
  "items": [
    {
      "client_id": "docs-ssl",
      "outcome": "resolved",
      "candidates": [{
        "entity_ref": "qprop_00002606cee96372585578d3ec315b5d6a1b1213ddd998e2734b3ad46e114987",
        "property_ref": "qprop_00002606cee96372585578d3ec315b5d6a1b1213ddd998e2734b3ad46e114987",
        "entity_kind": "tax_account",
        "status": "current",
        "area_uid": "area_us_dc",
        "match_basis": "identifier",
        "precision": null,
        "method": null,
        "canonical_identity": { "ssl": "0484--2250", "account_id": 203149, "identifiers": [ { "namespace": "dc_ssl", "raw_value": "04842250" } ] }
      }]
    },
    {
      "client_id": "docs-address",
      "outcome": "resolved",
      "candidates": [
        { "entity_ref": "qprop_fbc19d2e1d64c54e97709ddc024f20456d1f40471db40138f8ee0e94a5758fbb",
          "property_ref": "qprop_fbc19d2e1d64c54e97709ddc024f20456d1f40471db40138f8ee0e94a5758fbb",
          "entity_kind": "tax_account", "match_basis": "address_to_property",
          "precision": "contextual", "method": "contextual_parent_address" },
        { "entity_ref": "qentity_ead0a7baf2ae5925b5a0a09a22ba8c3c",
          "entity_kind": "parcel", "match_basis": "address_to_parcel",
          "precision": "contextual", "method": "contextual_parent_address" }
      ],
      "address_resolution": {
        "outcome": "resolved", "precision": "contextual", "method": "contextual_parent_address",
        "parcel_count": 1, "address_count": 1,
        "normalized_input": { "line": "1477 Newton St NW", "unit": "402", "normalized_line": "1477 NEWTON ST NW" }
      }
    }
  ]
}

get_entity

GET /api/v2/entities/{entity_ref} · $0.05 Reads one canonical entity of any kind. Unknown references return HTTP 404 not_found. Response data.entity

Field	Meaning
`entity_ref`, `entity_kind`, `area_uid`, `generation_id`, `status`	Identity and lifecycle (`current`, `retired`, `superseded`)
`identifiers[]`	Official identifiers with `authority_uid`, `namespace`, `raw_value`, `normalized_value`, validity dates and `status`
`attributes`	Kind-specific attributes; addresses and units carry a structured `address` object
`source_refs[]`	Canonical evidence references for the identifiers
`coverage_status`	`available` or `retired`

curl https://portal.quoindata.com/api/v2/entities/qentity_0000181b67f859019efe1b488b88b1f0 \
  -H "Authorization: Bearer $QUOIN_API_KEY"

{
  "entity": {
    "entity_ref": "qentity_0000181b67f859019efe1b488b88b1f0",
    "entity_kind": "unit",
    "area_uid": "area_us_dc",
    "generation_id": "7",
    "status": "current",
    "identifiers": [{ "authority_uid": "auth_dc_mar", "namespace": "mar", "raw_value": "158900", "status": "current" }],
    "attributes": {
      "address": { "address_line": "1477 NEWTON STREET NW", "address_normalized": "1477 NEWTON ST NW",
                   "unit": "402", "locality": "WASHINGTON", "region": "DC", "address_kind": "unit" }
    },
    "source_refs": ["qev1.i.1.193.0e2a54ed…"],
    "coverage_status": "available"
  }
}

traverse_relationships

GET /api/v2/entities/{entity_ref}/relationships · $0.05 per page Walks sourced relationships from a starting entity.

Query parameter	Default	Range
`direction`	`out`	`out`, `in`, `both`
`predicates`	all	Up to 50 relationship kinds, comma-separated or repeated
`max_depth`	1	1–3
`max_nodes`	200	1–200
`max_edges`	200	1–200
`limit`	20	1–100 nodes and edges per page
`cursor`		From `meta.next_cursor`

Relationship kinds in the current publication and their direction:

Predicate	Subject → Object	Count
`address_for_parcel`	address or unit → parcel	432,567
`account_for_parcel`	tax account → parcel	191,775

Because edges point toward parcels, use direction=out from an address, unit or tax account and direction=in (or both) from a parcel. About 12% of active tax accounts have no accepted parcel link in the current publication; traversing from them returns the root node and no edges. Response data

Field	Meaning
`root_ref`, `depth`	Echo of the request
`nodes[]`	`entity_ref`, `entity_kind`, `status`, `depth`, `canonical_identity`
`edges[]`	`relationship_ref`, `subject_ref`, `predicate`, `object_ref`, `direction`, `precision`, `method`, `confidence`, `status`, `generation_id`, `source_refs[]`
`max_nodes`, `max_edges`	Bounds applied

curl "https://portal.quoindata.com/api/v2/entities/qentity_0000181b67f859019efe1b488b88b1f0/relationships?direction=out&max_depth=2&limit=20" \
  -H "Authorization: Bearer $QUOIN_API_KEY"

{
  "root_ref": "qentity_0000181b67f859019efe1b488b88b1f0",
  "depth": 2,
  "nodes": [
    { "entity_ref": "qentity_0000181b67f859019efe1b488b88b1f0", "entity_kind": "unit", "depth": 0, "status": "current" },
    { "entity_ref": "qentity_ead0a7baf2ae5925b5a0a09a22ba8c3c", "entity_kind": "parcel", "depth": 1, "status": "current" }
  ],
  "edges": [{
    "relationship_ref": "qrel_88505784b8b3069d1e5e6eea1844035ce820cbfa7951a9dcdc43e0d4160345e8",
    "subject_ref": "qentity_0000181b67f859019efe1b488b88b1f0",
    "predicate": "address_for_parcel",
    "object_ref": "qentity_ead0a7baf2ae5925b5a0a09a22ba8c3c",
    "direction": "out",
    "precision": "contextual",
    "method": "contextual_parent_address",
    "confidence": 1,
    "status": "current",
    "generation_id": "7",
    "source_refs": ["qev1.r.d60e1625-…"]
  }],
  "max_nodes": 200,
  "max_edges": 200
}

search_properties

POST /api/v2/property-searches · $0.05 per page Bounded, deterministic search over entities of one kind in one area. Request body

Field	Type	Notes
`area_uid`	required	`area_us_dc`
`subject_kind`	required	`property`, `tax_account`, `parcel`, `address`, `unit`, `building`, `land_interest`
`area_relation`	default `located_in`	`located_in`, `taxed_in`, `assessed_in`, `served_by`, `permitted_by`
`filters[]`	up to 100	`{ field, value }` with `field` in `entity_ref`, `property_ref`, `address`
`sort`	required	`{ field, direction }`; `field` in `entity_ref`, `property_ref`, `address`; `direction` `asc` (default) or `desc`
`projection`	default `identity_summary`	`fact_summary` is reserved and returns HTTP 422 `unavailable`
`limit`, `cursor`		Pagination

Filter semantics:

entity_ref / property_ref: exact match. Two different reference filters in one request match nothing.
address: case-insensitive prefix on the normalized address. Punctuation, extra whitespace, street suffixes (Street → ST) and quadrant words are normalized; %, _ and \ are literal. Matching rows return the canonical address in canonical_identity.address.
Sorting by address requires an address filter; an unfiltered address sort returns HTTP 400 invalid_request.

Ordering is stable with entity_ref as the tie-breaker, so pages never duplicate or skip records. Response data

Field	Meaning
`items[]`	`entity_ref`, `entity_kind`, `status`, `area_uid`, `canonical_identity`, `subject_kind`, and `property_ref` when supported
`projection`	Echo

{
  "area_uid": "area_us_dc",
  "subject_kind": "tax_account",
  "filters": [{ "field": "address", "value": "1477 NEWTON ST" }],
  "sort": { "field": "address", "direction": "asc" },
  "limit": 20
}

{
  "items": [{
    "entity_ref": "qprop_fbc19d2e1d64c54e97709ddc024f20456d1f40471db40138f8ee0e94a5758fbb",
    "property_ref": "qprop_fbc19d2e1d64c54e97709ddc024f20456d1f40471db40138f8ee0e94a5758fbb",
    "entity_kind": "tax_account",
    "status": "current",
    "area_uid": "area_us_dc",
    "canonical_identity": { "ssl": "2681--0698", "address": "1477 NEWTON ST NW", "account_id": 23910 }
  }],
  "projection": "identity_summary"
}

Unfiltered listing ("filters": [], sort by entity_ref) is supported and is how you enumerate an area; use the cursor to continue.

get_property

POST /api/v2/property-queries · $0.05 per call Reads the record sections of up to five tax accounts. Request body

Field	Type	Notes
`property_refs[]`	1–5 `qprop_` references	From resolve or search
`sections[]`	optional	Default: all 13. Any of `identity`, `assessment`, `tax`, `delinquency_tax_sale`, `special_assessment`, `ownership`, `transfer`, `deed_reference`, `permit`, `license`, `inspection_enforcement`, `building`, `land`
`section_limit`	1–100, default 20	Maximum records per section
`fields`, `as_of`, `publication_id`, `cursors`	reserved	Return HTTP 422 `unavailable`

Response data.items[]

Field	Meaning
`property_ref`, `subject_kind`, `outcome`	`outcome` is `ok` or an explicit per-item failure
`sections.<name>`	Each section has `availability`, a records array named for the section (`assessments`, `sale_history`, `records`, …), `has_more` and `next_cursor` (always `null`, see below). Record sections also carry `status` and `limitations[]`; `identity` carries neither

Source-backed values are { value, status, source_refs[] } triples; status is reported when the value is taken directly from the source, and source_refs feed get_evidence. Record metadata such as stage, tax_year and record_date, and the whole identity section, are plain values. There is no continuation inside a section. When has_more is true, next_cursor is null and meta.truncated is true; the only way to see more records is a larger section_limit, up to 100. Treat a section as bounded, not complete. The response is also capped at 256 KiB; five accounts with all sections and section_limit 100 will exceed it and arrays are shortened. Ask for the sections you need.

{
  "property_refs": ["qprop_fbc19d2e1d64c54e97709ddc024f20456d1f40471db40138f8ee0e94a5758fbb"],
  "sections": ["identity", "assessment", "transfer"],
  "section_limit": 2
}

{
  "items": [{
    "property_ref": "qprop_fbc19d2e1d64c54e97709ddc024f20456d1f40471db40138f8ee0e94a5758fbb",
    "subject_kind": "tax_account",
    "outcome": "ok",
    "sections": {
      "identity": {
        "availability": "available",
        "records": [{ "ssl": "2681--0698", "account_id": 23910, "address": "1477 NEWTON ST NW WASHINGTON DC 20010" }],
        "has_more": false
      },
      "assessment": {
        "availability": "available", "status": "resolved", "has_more": true,
        "assessments": [{
          "stage": "current", "tax_year": 2026, "record_date": "2026-04-15",
          "land_value_dollars":        { "value": 1029900, "status": "reported", "source_refs": ["itspe_current|23911|assessment.current.land_value|26810698"] },
          "improvement_value_dollars": { "value": 1703810, "status": "reported", "source_refs": ["itspe_current|23911|assessment.current.improvement_value|26810698"] },
          "total_value_dollars":       { "value": 2733710, "status": "reported", "source_refs": ["itspe_current|23911|assessment.current.total_value|26810698"] }
        }],
        "limitations": ["Prior, current, and proposed are distinct source stages…"]
      },
      "transfer": {
        "availability": "available", "status": "resolved",
        "sale_history": [{
          "sale_date":          { "value": "2020-02-20", "status": "reported", "source_refs": ["cama_sales_current|476538993|sale.history.date|26810698"] },
          "sale_price_dollars": { "value": 0, "status": "reported", "source_refs": ["cama_sales_current|476538993|sale.history.price|26810698"] },
          "quality_flags": ["nominal_or_non_market_zero_price", "unqualified_sale"]
        }],
        "limitations": ["CAMA sale history is not a Recorder of Deeds chain of title, title report, or lien search."]
      }
    }
  }]
}

Assessment stages are prior (TY2025), current (TY2026) and proposed (TY2027), exactly as the Office of Tax and Revenue publishes them. The API does not interpolate or treat a proposed value as final.

get_evidence

POST /api/v2/evidence-lookups · $0.05 per call Expands source references into the official record they came from and a human verification route. Request body

Field	Type
`source_refs[]`	1–50 references taken from any response
`include_verification_routes`	boolean, default true

Response data

Field	Meaning
`evidence[]`	One item per reference. Legacy field references return `publisher`, `dataset_name`, `field_key`, `source_class`, `provenance` (dataset SHA-256, retrieval time, source record id, limitations) and `human_verification`. Canonical references (`qev1.…`) return `source_id`, `source_release_id`, `source_record_key`, `source_row_sha256`, the dated `claim`, and for relationships the full `relationship`
`verification_routes[]`	Portal name, link, ordered steps, exact lookup inputs, which `source_refs` and fields the route covers, and `property_link_scope` (`exact_property` or a contextual scope)
`verification_policy`	Always “Only official human-facing verification routes are returned.”

A reference that cannot be resolved does not fail the call: the item carries outcome: "invalid_reference" or "not_found" and the envelope status is partial.

{ "source_refs": ["itspe_current|203150|assessment.current.total_value|04842250"] }

{
  "evidence": [{
    "source_ref": "itspe_current|203150|assessment.current.total_value|04842250",
    "field_key": "assessment.current.total_value",
    "publisher": "DC Office of Tax and Revenue",
    "dataset_name": "Integrated Tax System Property Extract",
    "source_class": "official_snapshot",
    "provenance": {
      "source_record_id": 203150,
      "source_sha256": "6feca10ca22887dbb5be66c6bb9d12c19625c48291a0f54db96fa95cb46de86e",
      "dataset_retrieved_at": "2026-09-02T03:07:09.795435+00:00",
      "source_limitations": "Record dates vary by row. Retrieval date is not the fact effective date."
    },
    "human_verification": {
      "portal_name": "MyTax.DC.gov Real Property Search",
      "portal_url": "https://mytax.dc.gov/_/#2",
      "search_inputs": { "ssl": "0484--2250", "property_address": "555 MASSACHUSETTS AVE NW UNIT P-4, Washington, DC" },
      "steps": ["Open the MyTax.DC.gov Real Property Search.", "Enter the supplied property address or SSL and select Search.", "…"]
    }
  }],
  "verification_routes": [{
    "title": "MyTax.DC.gov Real Property Search",
    "link": "https://mytax.dc.gov/_/?Link=PropertySearch",
    "covers": ["Current assessment"],
    "covered_fields": ["assessment.current.total_value"],
    "property_link_scope": "exact_property",
    "lookup": { "ssl": "0484--2250" }
  }],
  "verification_policy": "Only official human-facing verification routes are returned."
}

The live portal may be newer than the dated extract the fact came from. Compare the cited record date, not only the value.

Get started

Using the API

get_catalog

resolve_entities

get_entity

traverse_relationships

search_properties

get_property

get_evidence

​get_catalog

​resolve_entities

​get_entity

​traverse_relationships

​search_properties

​get_property

​get_evidence

get_catalog

resolve_entities

get_entity

traverse_relationships

search_properties

get_property

get_evidence