Calibrated Similarity Search API

{
  "name": "Calibrated Similarity Search API",
  "description": "Stateless NMI + cosine fusion with entropy-driven alpha calibration",
  "url": "https://similarity-search-api-production.up.railway.app",
  "version": "1.0.0",
  "documentationUrl": "https://similarity-search-api-production.up.railway.app/docs",
  "provider": {
    "organization": "nexus-mcp-infra",
    "url": "https://github.com/nexus-mcp-infra/similarity-search-api-sdk"
  },
  "capabilities": {
    "streaming": false,
    "pushNotifications": false,
    "stateTransitionHistory": false
  },
  "defaultInputModes": [
    "application/json"
  ],
  "defaultOutputModes": [
    "application/json"
  ],
  "additionalInterfaces": [
    {
      "url": "https://similarity-search-api-production.up.railway.app/mcp",
      "transport": "MCP"
    }
  ],
  "securitySchemes": {
    "apiKeyHeader": {
      "type": "apiKey",
      "in": "header",
      "name": "X-API-Key"
    },
    "x402Payment": {
      "type": "apiKey",
      "in": "header",
      "name": "X-PAYMENT",
      "description": "x402 payment proof (USDC, Base Sepolia testnet) required on paid operations -- not a classic auth scheme."
    }
  },
  "security": [
    {
      "apiKeyHeader": [],
      "x402Payment": []
    }
  ],
  "skills": [
    {
      "id": "nexus_similarity_search_api_rank_items_by_nmi_cosine_fusion",
      "name": "NMI-Cosine Fused Similarity Ranking",
      "description": "Ranks a corpus of items against a query vector using a calibrated fusion score (alpha * cosine + (1-alpha) * NMI_normalizado), where alpha is auto-derived from the corpus's marginal entropy unless overridden. Results are identified by their 0-indexed position in corpus_vectors (this tool does not accept explicit item IDs). Requires a valid api_key (same as X-API-Key) and an x402 payment.",
      "tags": [
        "similarity-search",
        "embeddings",
        "nmi",
        "cosine-similarity"
      ]
    },
    {
      "id": "nexus_similarity_search_api_estimate_corpus_entropy_profile",
      "name": "Corpus Entropy and Calibrated Alpha Estimator",
      "description": "Computes the aggregate entropy-calibrated alpha for a corpus without running a full search -- useful to inspect before committing to a large rank_items_by_nmi_cosine_fusion call. Returns a single aggregate corpus_entropy value, not a per-dimension breakdown. Requires a valid api_key (same as X-API-Key) and an x402 payment.",
      "tags": [
        "entropy",
        "calibration"
      ]
    },
    {
      "id": "nexus_similarity_search_api_score_pair_nmi_cosine",
      "name": "Single-Pair NMI-Cosine Scorer",
      "description": "Computes the NMI-cosine fusion score for exactly one (query, target) vector pair at a fixed alpha. Use for explainability, debugging, or unit-level validation of fusion scores before running full corpus ranking. Requires a valid api_key (same as X-API-Key) and an x402 payment.",
      "tags": [
        "similarity-search",
        "debugging"
      ]
    }
  ],
  "metadata": {
    "protocol_note": "This service implements the Model Context Protocol (MCP) at /mcp, not A2A's own JSONRPC/gRPC/HTTP+JSON task methods (message/send, tasks/get, etc.). This Agent Card is provided for discovery/indexing purposes; A2A-conformant task orchestration is not implemented."
  }
}