# io.github.nexus-mcp-infra/similarity-search-api-sdk (remote · similarity-search-api-production.up.railway.app)

Stateless NMI + cosine fusion with entropy-driven alpha calibration

- Trust score: 63/100 (medium)
- Change this week: +4
- Registry status: active
- Liveness: live
- Owner verified: no
- Last scored: 2026-08-03

## Components

- remote · `similarity-search-api-production.up.railway.app`: 63/100 (this document), [markdown](https://verifymcp.io/servers/nexus-mcp-infra-similarity-search-api-sdk/similarity-search-api-production.md), [page](https://verifymcp.io/servers/nexus-mcp-infra-similarity-search-api-sdk/similarity-search-api-production)

## Channel facts

- Endpoint: `https://similarity-search-api-production.up.railway.app/mcp`
- Transports: `streamable-http`
- Auth: `none`
- Version: `1.0.0`

## Trust breakdown

How this component scores in each security and reliability category. Every signal is checked automatically against the live server, and we only credit what we can confirm. Scores are 0–100 per category. Scoring method: https://verifymcp.io/docs/scoring (what has changed: https://verifymcp.io/docs/scoring/changelog)

Scored 2026-08-03.

- **Endpoint Security**: 57/100
  - The endpoint's TLS certificate is valid, in date, and uses a strong key.
  - Authorisation not fully verified: no authorisation is required to call this server, and 3 tool(s) never declared a destructiveHint. The MCP spec treats an absent hint as destructive by default, so we cannot call this surface safe.
  - HTTPS is enforced; there's no plaintext access path.
  - HSTS check failed: the Strict-Transport-Security header is absent.
  - DNSSEC check failed: this domain isn't protected by DNSSEC.
- **Transport & Reachability**: 100/100
  - Verified streamable-http transport via a live MCP handshake.
- **Schema Quality & AI Usability**: 55/100
  - AI-judged instruction clarity (good).
  - Context-footprint check failed: tool/resource definitions use about 964 tokens (~321/item across 3 items; 3 tools + 0 resources), over budget; trim descriptions and params.
  - Usage-examples check failed: none of the tools include examples.
- **Stability & Change Management**: 27/100
  - Stability observed for 8 of 30 days with no destabilising changes; credit accrues until the full window elapses.
- **Tool Coverage**: 100/100
  - 100% of tools have a non-trivial description (not blank, and not just the tool's name).
  - 100% of tool parameters carry a description.
  - Structured output schemas are declared (100% of tools); any adoption earns full credit.
- **Capabilities**: 100/100
  - Implements a supported MCP spec version (2025-11-25); the latest is 2026-07-28.

## Install

### Claude

```bash
claude mcp add --transport http nexus-mcp-infra-similarity-search-api-sdk https://similarity-search-api-production.up.railway.app/mcp
```

### Codex

```toml
[mcp_servers.nexus-mcp-infra-similarity-search-api-sdk]
url = "https://similarity-search-api-production.up.railway.app/mcp"
```

### opencode

```json
{
  "$schema": "https://opencode.ai/config.json",
  "mcp": {
    "nexus-mcp-infra-similarity-search-api-sdk": {
      "type": "remote",
      "url": "https://similarity-search-api-production.up.railway.app/mcp",
      "enabled": true
    }
  }
}
```

### OpenClaw

```bash
openclaw mcp add nexus-mcp-infra-similarity-search-api-sdk --url https://similarity-search-api-production.up.railway.app/mcp --transport streamable-http
```

### Hermes

```yaml
mcp_servers:
  nexus-mcp-infra-similarity-search-api-sdk:
    url: "https://similarity-search-api-production.up.railway.app/mcp"
```

### Other

```json
{
  "mcpServers": {
    "nexus-mcp-infra-similarity-search-api-sdk": {
      "type": "http",
      "url": "https://similarity-search-api-production.up.railway.app/mcp"
    }
  }
}
```

The mcpServers block is a cross-client convention. Remote transports vary, so check your client's docs.

## Changelog

Every change recorded for this component, newest first. Days that predate change tracking, or that we cannot explain, say so: "we were watching and nothing happened" and "we were not watching" are different claims.

### 2026-08-03 (score 63, +1)

No change was recorded against any check on this day. Stability & Change Management went from 23 to 27. That category is still filling its 30-day observation window: 7 days of observed history at the previous scan, 8 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-08-01 (score 62, +1)

No change was recorded against any check on this day. Stability & Change Management went from 17 to 20. That category is still filling its 30-day observation window: 5 days of observed history at the previous scan, 6 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-07-31 (score 61, 0)

- [functional] We updated how we score, so this day's move reflects our rubric, not a change to the server

### 2026-07-30 (score 61, +1)

- [functional] We updated how we score, so this day's move reflects our rubric, not a change to the server

### 2026-07-29 (score 60, +1)

No change was recorded against any check on this day. Stability & Change Management went from 7 to 10. That category is still filling its 30-day observation window: 2 days of observed history at the previous scan, 3 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-07-27 (score 59, +1)

- [functional] We updated how we score, so this day's move reflects our rubric, not a change to the server

### 2026-07-26 (score 58)

First indexed and scored.

## MCP tools (3)

### `nexus_similarity_search_api_rank_items_by_nmi_cosine_fusion` (~399 tokens)

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). Use this when you need semantically-calibrated similarity over a stateless corpus of up to 500k items without a vector database. Do NOT use for purely geometric nearest-neighbor search where NMI overhead is unnecessary, nor for corpora larger than 500k items per call. Requires a valid api_key (same as X-API-Key) and an x402 payment.

Input parameters:

- `alpha_override` (number): Fixed alpha weight for cosine component in [0.0, 1.0]. If omitted, alpha is auto-calibrated from corpus entropy. Set to 1.0 to use pure cosine; 0.0 for pure NMI.
- `api_key` (string, required): API key required for this paid operation -- same secret configured as X-API-Key on the REST endpoints (SIMILARITY_API_KEY). Payment (x402) alone is not sufficient; both gates must pass.
- `corpus_vectors` (array, required): List of dense numeric vectors forming the corpus to rank against. Each inner array must match query_vector dimensionality. Maximum 500000 entries.
- `n_bins` (number): Number of histogram bins used to discretize continuous dimensions when estimating NMI. Must be between 3 and 50.
- `query_vector` (array, required): Dense numeric vector representing the query item. Must have the same dimensionality as all corpus_vectors entries.
- `top_k` (number): Number of top-ranked results to return, ordered by descending fusion score. Capped at 1000 by the core service regardless of corpus size.

### `nexus_similarity_search_api_estimate_corpus_entropy_profile` (~253 tokens)

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 -- the real logic only exposes the mean marginal entropy across dimensions, not H(X_d) per individual dimension. Do NOT use expecting per-dimension granularity. Requires a valid api_key (same as X-API-Key) and an x402 payment.

Input parameters:

- `api_key` (string, required): API key required for this paid operation -- same secret configured as X-API-Key on the REST endpoints (SIMILARITY_API_KEY). Payment (x402) alone is not sufficient; both gates must pass.
- `corpus_vectors` (array, required): List of dense numeric vectors for which to compute the aggregate entropy and calibrated alpha. Each inner array must be the same length. Maximum 500000 entries.
- `n_bins` (number): Number of histogram bins for entropy discretization. Must be between 3 and 50; should match the n_bins used in rank_items_by_nmi_cosine_fusion for the profile to be consistent.

### `nexus_similarity_search_api_score_pair_nmi_cosine` (~312 tokens)

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. Unlike corpus-level ranking, alpha is NOT auto-calibrated for a single pair -- the real logic requires a fixed alpha (default 0.5); pass alpha explicitly for a specific blend. Do NOT use in a loop to score many pairs; batch them into rank_items_by_nmi_cosine_fusion instead. Requires a valid api_key (same as X-API-Key) and an x402 payment.

Input parameters:

- `alpha` (number): Fixed alpha weight for the cosine component in [0.0, 1.0], applied as-is -- not auto-calibrated. Default 0.5 matches the core service default.
- `api_key` (string, required): API key required for this paid operation -- same secret configured as X-API-Key on the REST endpoints (SIMILARITY_API_KEY). Payment (x402) alone is not sufficient; both gates must pass.
- `n_bins` (number): Histogram bins for NMI discretization. Must be between 3 and 50.
- `vector_a` (array, required): First dense numeric vector of the pair. Must have the same dimensionality as vector_b.
- `vector_b` (array, required): Second dense numeric vector of the pair. Must have the same dimensionality as vector_a.

## Diagnostics

Captured diagnostic sections: TLS, DNSSEC, Authorisation, Transports. The full working is on the page: https://verifymcp.io/servers/nexus-mcp-infra-similarity-search-api-sdk/similarity-search-api-production#diagnostics

## Score history

- 2026-08-03: 63
- 2026-08-02: 62
- 2026-08-01: 62
- 2026-07-31: 61
- 2026-07-30: 61
- 2026-07-29: 60
- 2026-07-28: 59
- 2026-07-27: 59
- 2026-07-26: 58

## Links

- Remote endpoint: https://similarity-search-api-production.up.railway.app/mcp
- Repository: https://github.com/nexus-mcp-infra/similarity-search-api-sdk
- Changelog RSS feed: https://verifymcp.io/servers/nexus-mcp-infra-similarity-search-api-sdk/similarity-search-api-production/changelog.xml
- Changelog JSON feed: https://verifymcp.io/servers/nexus-mcp-infra-similarity-search-api-sdk/similarity-search-api-production/changelog.json
- HTML version of this page: https://verifymcp.io/servers/nexus-mcp-infra-similarity-search-api-sdk/similarity-search-api-production