Agent & Developer APIs

1. Content Negotiation (Markdown)

Every card, sealed product, and knowledge base detail page supports standard HTTP header negotiation. Send `Accept: text/markdown` or check our fallback file pointers in the header link headers.

GET /knowledge/card-grading-guide-psa-scale HTTP/1.1
Host: getcardvalue.com
Accept: text/markdown

Response Headers:
Content-Type: text/markdown; charset=utf-8
x-markdown-tokens: 280

2. Knowledge Base Query API

Retrieve the full knowledge category layout, or query by Meituan facet tag keys or query string.

GET /api/knowledge?q=grading&tag=stable-value HTTP/1.1
Host: getcardvalue.com

Response:
[
  {
    "id": "card-grading-guide-psa-10-multiplier",
    "question": "What is the significance of the PSA 10 Value Multiplier?",
    "answer": "...",
    "facility_tags": ["climate-controlled"],
    "structured": {
      "comps": {
        "psa_10_multiplier": 2.7
      }
    }
  }
]

3. Single Article Fetch API

GET /api/knowledge/card-grading-guide-psa-scale HTTP/1.1
Host: getcardvalue.com

Response:
{
  "id": "card-grading-guide-psa-scale",
  "question": "...",
  "answer_detail": "...",
  "last_verified": "2026-06-28",
  "structured": { ... }
}