> ## Documentation Index > Fetch the complete documentation index at: https://crushrewards.dev/docs/llms.txt > Use this file to discover all available pages before exploring further. # Measure how concentrated a category is > How concentrated or fragmented a category is: HHI on the standard 0-10,000 scale, CR4 (the combined share of the four largest brands), the effective number of brands, and a plain-language label. Answers 'is this category competitive or dominated', 'how many real players are there', and 'what is the market structure'. Computed over the same brand vector share-of-shelf returns, so the two answers can never disagree about who is on the shelf. The HHI bands follow the US DOJ/FTC Horizontal Merger Guidelines (under 1,500 competitive; 1,500-2,500 moderately concentrated; above 2,500 highly concentrated). Effective brands is 1/HHI expressed as a count and is fractional by nature - fifty brands where one holds 90% is not a fifty-brand market, and this reports roughly 1.2. Every metric is withheld together (all null) below five brands, because a concentration figure over three brands describes who happens to be in the catalog rather than who competes. ## OpenAPI ````yaml https://api.syntalic.com/openapi.json get /v1/analyst/category-concentration openapi: 3.1.0 info: title: 'Syntalic — Data Analytics for Agentic Commerce ' version: 1.0.0 contact: name: Syntalic email: support@syntalic.com url: https://syntalic.com description: >- Competitive pricing data across US and Canadian e-commerce retailers (Amazon, Walmart, Target, Best Buy, Home Depot, etc.). Serves price comparisons, deal alerts, brand tracking, promotional intelligence, and market analytics to AI agents via x402 and MPP micropayments. x-guidance: >- This API has three endpoint groups organized by use case: **Shopper endpoints** ($0.01/query): Use these for price comparisons and deal hunting. Start with /v1/shopper/best-price?q= to find the cheapest option across retailers. Use /v1/shopper/deal-finder?category= to find discounted products. Use /v1/shopper/price-drop-alert?q= to check for recent price drops. **Marketing endpoints** ($0.01/query): Use these for competitive analysis. /v1/marketing/competitive-landscape?category= shows all products in a category with pricing. /v1/marketing/brand-tracker?brand= tracks a brand's pricing over time. /v1/marketing/share-of-shelf?category= shows brand market share. **Analyst endpoints** ($0.02/query): Use these for market-level insights. /v1/analyst/inflation?category= shows price trends over time. /v1/analyst/price-dispersion?category= shows price spread across retailers. All endpoints accept an optional 'country' parameter (us or ca, defaults to us). Query parameters use 'q' for free-text search and 'category' for category-level queries. Marketing and analyst responses carry a `meta` block (served_from, freshness_seconds, schema_version) for staleness budgeting and a `resolved` block describing how the category input was matched against the taxonomy. Every response also sends an X-Data-Freshness-Hours header. **Free pre-payment rejection:** requests that cannot be served are rejected BEFORE any payment challenge — invalid params (400 INVALID_PARAMS), retailers that are not serving-eligible (404 RETAILER_NOT_SERVING_ELIGIBLE, with the catalog quality status and the serving_eligible_retailers list in error.details), and shopper queries that resolve to nothing in the catalog (404 NO_RESULTS). You only pay when the API can actually execute your query. Retailer values are case-insensitive (amazon == Amazon). servers: - url: https://api.syntalic.com security: [] paths: /v1/analyst/category-concentration: get: tags: - Analyst summary: Measure how concentrated a category is description: >- How concentrated or fragmented a category is: HHI on the standard 0-10,000 scale, CR4 (the combined share of the four largest brands), the effective number of brands, and a plain-language label. Answers 'is this category competitive or dominated', 'how many real players are there', and 'what is the market structure'. Computed over the same brand vector share-of-shelf returns, so the two answers can never disagree about who is on the shelf. The HHI bands follow the US DOJ/FTC Horizontal Merger Guidelines (under 1,500 competitive; 1,500-2,500 moderately concentrated; above 2,500 highly concentrated). Effective brands is 1/HHI expressed as a count and is fractional by nature - fifty brands where one holds 90% is not a fifty-brand market, and this reports roughly 1.2. Every metric is withheld together (all null) below five brands, because a concentration figure over three brands describes who happens to be in the catalog rather than who competes. operationId: getCategoryConcentration parameters: - name: category in: query required: true schema: type: string minLength: 1 description: >- Product category. Accepts a human-readable name (e.g. 'electronics', 'beauty') or a taxonomy slug path (e.g. 'electronics/headphones'); matched against the catalog's category tree (exact node, subtree, or path substring). Also accepts a GS1 GPC code (exactly 8 digits, e.g. '10001159') to filter by PRODUCT TYPE instead of by shelf placement — the same product type is shelved under different categories by different retailers, so a category filter answers from a fraction of the data while a GPC code spans them. Coarser codes (class/family/segment) match every brick beneath them. Resolve a phrase to a code with /v1/reference/classify?q=... ; when a code is used, resolved.match_source is 'gpc'. example: electronics - name: country in: query required: false schema: type: string enum: - us - ca default: us description: Country (us or ca) example: us responses: '200': description: Category concentration content: application/json: schema: type: object properties: category: type: string country: type: string hhi: type: integer nullable: true cr4: type: number nullable: true effective_brands: type: number nullable: true fragmentation: type: string nullable: true brand_count: type: integer top_shares: type: array items: type: object properties: brand: type: string share_pct: type: number coverage: type: object description: >- How much data backed this answer. `sufficient` is false when the slice is too thin to read as a market statement; the count is always reported so you can judge for yourself, and `note` explains an empty or thin result rather than leaving you to infer it. properties: products: type: integer example: 42 sufficient: type: boolean example: true note: type: string unpublished_note: type: string description: >- Names columns that came back null on EVERY row because the publish job writes them unpopulated, not because the subjects lack the attribute. Never infer a zero or an absence from a column named here. sku_note: type: string description: >- Present when `skus` is null on every row returned. Read the column as unavailable for this run, not as a stocking fact. rank_note: type: string description: >- Present when brands carry `tied_with`. Says how many, and that the tie list is pairwise proximity rather than an equivalence class. additionalProperties: true freshness: type: object description: >- How current the underlying observations are. `observedThrough` is the newest observation behind this answer; `staleHours` is its age. Both null when nothing was observed. properties: observedThrough: type: string format: date-time nullable: true staleHours: type: number nullable: true example: 6.5 additionalProperties: true quality: type: object additionalProperties: true nullable: true resolved: type: object properties: input: type: string category_path: type: string nullable: true department: type: string nullable: true match_source: type: string nullable: true match_confidence: type: number nullable: true alternates: type: array items: type: object additionalProperties: true additionalProperties: true meta: type: object properties: served_from: type: string freshness_seconds: type: number schema_version: type: string computed_at: type: string format: date-time price_observed_at_min: type: string format: date-time nullable: true price_observed_at_max: type: string format: date-time nullable: true additionalProperties: true '400': description: >- Invalid query parameters or unsupported enum values. Rejected by preflight BEFORE the payment challenge — no payment is requested or charged for malformed requests. content: application/problem+json: schema: type: object required: - type - title - status properties: type: type: string format: uri-reference title: type: string example: Bad Request status: type: integer const: 400 detail: type: string instance: type: string error: type: object properties: code: type: string message: type: string details: type: object additionalProperties: true additionalProperties: true additionalProperties: true '402': description: Payment challenge required before executing paid work content: application/problem+json: schema: type: object required: - type - title - status properties: type: type: string format: uri-reference title: type: string example: Payment Required status: type: integer const: 402 detail: type: string instance: type: string error: type: object properties: code: type: string message: type: string details: type: object additionalProperties: true additionalProperties: true additionalProperties: true '404': description: >- No matching result. error.code distinguishes the cases: NO_RESULTS (the query resolves to nothing in the catalog), RETAILER_NOT_SERVING_ELIGIBLE (the requested retailer exists but is not serving-eligible — error.details carries its catalog quality_status and the serving_eligible_retailers list to retry against), or NOT_PUBLISHED (a social rollup the current publish run does not compute yet — a gap in what we publish, not a finding about the category). Structurally-unservable requests are rejected by preflight before any payment challenge. content: application/problem+json: schema: type: object required: - type - title - status properties: type: type: string format: uri-reference title: type: string example: Not Found status: type: integer const: 404 detail: type: string instance: type: string error: type: object properties: code: type: string message: type: string details: type: object additionalProperties: true additionalProperties: true additionalProperties: true '429': description: Rate limit exceeded content: application/problem+json: schema: type: object required: - type - title - status properties: type: type: string format: uri-reference title: type: string example: Too Many Requests status: type: integer const: 429 detail: type: string instance: type: string error: type: object properties: code: type: string message: type: string details: type: object additionalProperties: true additionalProperties: true additionalProperties: true '500': description: Unexpected server error content: application/problem+json: schema: type: object required: - type - title - status properties: type: type: string format: uri-reference title: type: string example: Internal Server Error status: type: integer const: 500 detail: type: string instance: type: string error: type: object properties: code: type: string message: type: string details: type: object additionalProperties: true additionalProperties: true additionalProperties: true ````