> ## Documentation Index > Fetch the complete documentation index at: https://docs.useboom.ai/llms.txt > Use this file to discover all available pages before exploring further. # Preview a segment filter > Count how many people currently match a filter, without saving. Use it to check the audience before saving a segment. ## OpenAPI ````yaml /api-reference/openapi.json post /api/v1/segments/preview openapi: 3.1.0 info: title: Boom API version: 1.0.0 description: >- Boom's public REST API — one uniform surface over every platform capability. CDP: upsert people and custom objects, define object and relationship types, link and unlink relationships, and record behavioral events — one record per request or up to 1000 per request via the `/batch` endpoints. Segments: read (list, read, membership) and full authoring — discover the filterable catalog, validate a filter, create and update segments, preview match counts, and trigger evaluation. Initiatives: create and configure outreach initiatives, link WhatsApp templates, drive the lifecycle (launch, cancel, archive), and read collected-data summaries. Participants: enroll people into an active initiative, track their status, read conversation transcripts, and stop outreach. Journeys: read-only access to always-on message flows and their metrics. WhatsApp templates: list your WhatsApp numbers and list, read, and create message templates. The same capabilities are exposed as MCP tools with identical schemas. servers: - url: https://www.useboom.ai description: Production - url: https://dev.useboom.ai description: Development (sandbox — use a development organization API key) security: - bearerAuth: [] paths: /api/v1/segments/preview: post: tags: - Segments summary: Preview a segment filter description: >- Count how many people currently match a filter, without saving. Use it to check the audience before saving a segment. operationId: segments_preview requestBody: required: true content: application/json: schema: $schema: https://json-schema.org/draft/2020-12/schema type: object properties: filterExpression: description: >- The audience filter: a tree of predicates over person attributes, related data, and events. Discover valid `attr` tokens and operators with segments_catalog (GET /api/v1/segments/catalog). type: object properties: kind: type: string const: person op: type: string enum: - AND - OR predicates: type: array items: oneOf: - type: object properties: kind: type: string const: has_relationship connector: type: string enum: - AND - OR customObjectType: type: string minLength: 1 attributeFilters: type: array items: type: object properties: attr: type: string path: minItems: 1 maxItems: 5 type: array items: type: string pattern: ^[A-Za-z_][A-Za-z0-9_]*$ type: type: string enum: - STRING - NUMBER - BOOLEAN - DATE - JSON - ARRAY op: type: string enum: - eq - neq - in - not_in - contains - not_contains - starts_with - ends_with - gt - gte - lt - lte - 'on' - before - after - between - in_last_n - in_next_n - more_than_n_ago - more_than_n_from_now - exactly_n_from_today - is_null - is_not_null value: anyOf: - type: string - type: number - type: boolean - type: array items: anyOf: - type: string - type: number - type: object properties: from: type: string to: type: string required: - from - to - type: object properties: amount: type: integer minimum: 1 maximum: 9999 unit: type: string enum: - days - weeks - months required: - amount - unit - type: object properties: daysOffset: type: integer minimum: -9007199254740991 maximum: 9007199254740991 rollForward: type: object properties: fromDow: type: integer minimum: 0 maximum: 6 includeDows: minItems: 1 type: array items: type: integer minimum: 0 maximum: 6 required: - fromDow - includeDows required: - daysOffset required: - attr - type - op path: minItems: 1 maxItems: 3 type: array items: type: object properties: customObjectType: type: string minLength: 1 direction: type: string enum: - parent_to_child - child_to_parent relationshipType: type: string minLength: 1 attributeFilters: type: array items: type: object properties: attr: type: string path: minItems: 1 maxItems: 5 type: array items: type: string pattern: ^[A-Za-z_][A-Za-z0-9_]*$ type: type: string enum: - STRING - NUMBER - BOOLEAN - DATE - JSON - ARRAY op: type: string enum: - eq - neq - in - not_in - contains - not_contains - starts_with - ends_with - gt - gte - lt - lte - 'on' - before - after - between - in_last_n - in_next_n - more_than_n_ago - more_than_n_from_now - exactly_n_from_today - is_null - is_not_null value: anyOf: - type: string - type: number - type: boolean - type: array items: anyOf: - type: string - type: number - type: object properties: from: type: string to: type: string required: - from - to - type: object properties: amount: type: integer minimum: 1 maximum: 9999 unit: type: string enum: - days - weeks - months required: - amount - unit - type: object properties: daysOffset: type: integer minimum: -9007199254740991 maximum: 9007199254740991 rollForward: type: object properties: fromDow: type: integer minimum: 0 maximum: 6 includeDows: minItems: 1 type: array items: type: integer minimum: 0 maximum: 6 required: - fromDow - includeDows required: - daysOffset required: - attr - type - op required: - customObjectType - attributeFilters required: - kind - customObjectType - attributeFilters - type: object properties: kind: type: string const: person_attribute connector: type: string enum: - AND - OR attr: type: string path: minItems: 1 maxItems: 5 type: array items: type: string pattern: ^[A-Za-z_][A-Za-z0-9_]*$ type: type: string enum: - STRING - NUMBER - BOOLEAN - DATE - JSON - ARRAY op: type: string enum: - eq - neq - in - not_in - contains - not_contains - starts_with - ends_with - gt - gte - lt - lte - 'on' - before - after - between - in_last_n - in_next_n - more_than_n_ago - more_than_n_from_now - exactly_n_from_today - is_null - is_not_null value: anyOf: - type: string - type: number - type: boolean - type: array items: anyOf: - type: string - type: number - type: object properties: from: type: string to: type: string required: - from - to - type: object properties: amount: type: integer minimum: 1 maximum: 9999 unit: type: string enum: - days - weeks - months required: - amount - unit - type: object properties: daysOffset: type: integer minimum: -9007199254740991 maximum: 9007199254740991 rollForward: type: object properties: fromDow: type: integer minimum: 0 maximum: 6 includeDows: minItems: 1 type: array items: type: integer minimum: 0 maximum: 6 required: - fromDow - includeDows required: - daysOffset required: - kind - attr - type - op - type: object properties: kind: type: string const: person_group connector: type: string enum: - AND - OR filters: minItems: 1 type: array items: type: object properties: attr: type: string path: minItems: 1 maxItems: 5 type: array items: type: string pattern: ^[A-Za-z_][A-Za-z0-9_]*$ type: type: string enum: - STRING - NUMBER - BOOLEAN - DATE - JSON - ARRAY op: type: string enum: - eq - neq - in - not_in - contains - not_contains - starts_with - ends_with - gt - gte - lt - lte - 'on' - before - after - between - in_last_n - in_next_n - more_than_n_ago - more_than_n_from_now - exactly_n_from_today - is_null - is_not_null value: anyOf: - type: string - type: number - type: boolean - type: array items: anyOf: - type: string - type: number - type: object properties: from: type: string to: type: string required: - from - to - type: object properties: amount: type: integer minimum: 1 maximum: 9999 unit: type: string enum: - days - weeks - months required: - amount - unit - type: object properties: daysOffset: type: integer minimum: -9007199254740991 maximum: 9007199254740991 rollForward: type: object properties: fromDow: type: integer minimum: 0 maximum: 6 includeDows: minItems: 1 type: array items: type: integer minimum: 0 maximum: 6 required: - fromDow - includeDows required: - daysOffset required: - attr - type - op required: - kind - filters - type: object properties: kind: type: string const: event connector: type: string enum: - AND - OR eventName: type: string minLength: 1 occurred: type: boolean propertyFilters: minItems: 1 type: array items: type: object properties: key: type: string minLength: 1 path: minItems: 1 maxItems: 5 type: array items: type: string pattern: ^[A-Za-z_][A-Za-z0-9_]*$ type: type: string enum: - STRING - NUMBER - BOOLEAN - DATE - JSON - ARRAY op: type: string enum: - eq - neq - in - not_in - contains - not_contains - starts_with - ends_with - gt - gte - lt - lte - 'on' - before - after - between - in_last_n - in_next_n - more_than_n_ago - more_than_n_from_now - exactly_n_from_today - is_null - is_not_null value: anyOf: - type: string - type: number - type: boolean - type: array items: anyOf: - type: string - type: number - type: object properties: from: type: string to: type: string required: - from - to - type: object properties: amount: type: integer minimum: 1 maximum: 9999 unit: type: string enum: - days - weeks - months required: - amount - unit - type: object properties: daysOffset: type: integer minimum: -9007199254740991 maximum: 9007199254740991 rollForward: type: object properties: fromDow: type: integer minimum: 0 maximum: 6 includeDows: minItems: 1 type: array items: type: integer minimum: 0 maximum: 6 required: - fromDow - includeDows required: - daysOffset required: - key - type - op window: type: object properties: op: type: string enum: - in_last_n - more_than_n_ago - between - before - after - 'on' value: anyOf: - type: string - type: number - type: boolean - type: array items: anyOf: - type: string - type: number - type: object properties: from: type: string to: type: string required: - from - to - type: object properties: amount: type: integer minimum: 1 maximum: 9999 unit: type: string enum: - days - weeks - months required: - amount - unit - type: object properties: daysOffset: type: integer minimum: -9007199254740991 maximum: 9007199254740991 rollForward: type: object properties: fromDow: type: integer minimum: 0 maximum: 6 includeDows: minItems: 1 type: array items: type: integer minimum: 0 maximum: 6 required: - fromDow - includeDows required: - daysOffset required: - op required: - kind - eventName - occurred required: - kind - op - predicates required: - filterExpression responses: '200': description: Success content: application/json: schema: $schema: https://json-schema.org/draft/2020-12/schema type: object properties: count: type: integer minimum: -9007199254740991 maximum: 9007199254740991 description: People currently matching the filter (capped when huge). required: - count additionalProperties: false '400': description: Validation failed or the request cannot proceed. content: application/json: schema: type: object properties: error: type: object properties: code: type: string description: Stable machine-readable error code (snake_case). message: type: string required: - code - message required: - error '401': description: Missing, malformed, or revoked API key. content: application/json: schema: type: object properties: error: type: object properties: code: type: string description: Stable machine-readable error code (snake_case). message: type: string required: - code - message required: - error '404': description: The resource does not exist in this organization. content: application/json: schema: type: object properties: error: type: object properties: code: type: string description: Stable machine-readable error code (snake_case). message: type: string required: - code - message required: - error '409': description: >- Conflicts with the current state (duplicates, wrong lifecycle state). content: application/json: schema: type: object properties: error: type: object properties: code: type: string description: Stable machine-readable error code (snake_case). message: type: string required: - code - message required: - error '422': description: The request is well-formed but semantically invalid. content: application/json: schema: type: object properties: error: type: object properties: code: type: string description: Stable machine-readable error code (snake_case). message: type: string required: - code - message required: - error '429': description: Rate limit exceeded — retry after `Retry-After`. content: application/json: schema: type: object properties: error: type: object properties: code: type: string description: Stable machine-readable error code (snake_case). message: type: string required: - code - message required: - error '500': description: Internal server error. content: application/json: schema: type: object properties: error: type: object properties: code: type: string description: Stable machine-readable error code (snake_case). message: type: string required: - code - message required: - error '503': description: Transient error — retry with a narrower request. content: application/json: schema: type: object properties: error: type: object properties: code: type: string description: Stable machine-readable error code (snake_case). message: type: string required: - code - message required: - error components: securitySchemes: bearerAuth: type: http scheme: bearer description: 'Organization API key, sent as `Authorization: Bearer boom_org_...`.' ````