vector-databases

vector-databases is a skill for Claude Code, Codex from LuuOW/meridian-mcp. It costs 71 tokens per session (2,659 once invoked), scanned A, original, MIT.

A guide to databases for meaning-based search, including Pinecone, Weaviate, Chroma, Qdrant, pgvector, and FAISS. It covers turning content into embeddings, finding similar items, combining keyword and meaning-based search, and building RAG systems.

In plain words
What is it for?
Use it to design embedding pipelines, configure vector indexes, add metadata filters and tenant namespaces, combine BM25 keyword search with semantic search, and connect retrieval to knowledge assistants.
Why use it?
It helps choose and tune the retrieval layer behind search and AI systems, balancing result quality, speed, memory use, and data separation.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one. Also seen: positional $N argument.

Good fit Use it to design embedding pipelines, configure vector indexes, add metadata filters and tenant namespaces, combine BM25 keyword search with semantic search, and connect retrieval to knowledge assistants.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/luuow/meridian-mcp/vector-databases
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent
npx skills add LuuOW/meridian-mcp --skill vector-databases
Clone the repo
git clone --depth 1 https://github.com/LuuOW/meridian-mcp

Made for: Claude Code, Codex.

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README.md
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Per session 71 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,659 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00071 $0.02659
Opus 5.5 $0.00028 $0.01064
Sonnet 5.5 $0.00014 $0.00532
Haiku 4.5 $0.00007 $0.00266

Measured 1mo ago against content hash 8609dc67ca0a, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

vector-databases scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 1mo ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

skills/vector-databases/SKILL.md · 102 lines

How it starts

The opening of the file, as written. The whole thing — 102 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Vector Databases

Vector databases are the retrieval layer for semantic search and RAG (Retrieval-Augmented Generation) systems, storing high-dimensional embedding vectors and enabling approximate nearest-neighbor (ANN) search at scale. This skill covers the full engineering stack: choosing and configuring a vector store, building embedding pipelines, tuning ANN indices for the accuracy/latency/memory trade-off, implementing hybrid retrieval, and wiring everything into production RAG architectures. It orbits the llm-integration and knowledge skills.

Core Concepts

Embedding Pipelines

Embeddings are the foundation — garbage in, garbage out. Model selection matters: text-embedding-3-large (OpenAI, 3072 dims, reducible via dimensions param), voyage-3 (Voyage AI, strong for code/technical), embed-english-v3.0 (Cohere, supports int8 quantization natively), nomic-embed-text-v1.5 (open-source, Matryoshka — supports variable output dims). For multilingual: multilingual-e5-large or Cohere's multilingual model.

Batching: always batch embedding calls. OpenAI allows up to 2048 inputs per call. Local models via sentence-transformers: model.encode(texts, batch_size=64, show_progress_bar=True, normalize_embeddings=True). Normalize to unit sphere if using cosine similarity (makes dot product equivalent, faster in FAISS/Qdrant).

Chunking strategy is retrieval-critical: fixed-size (512 tokens with 50-token overlap) works as a baseline. Semantic chunking (split on embedding similarity drops) improves coherence. For structured docs (PDFs, HTML), prefer element-aware chunking via unstructured library — respects headings, tables, lists. Store chunk_index and parent_doc_id as metadata to enable parent-document retrieval (fetch surrounding chunks at query time).

FAISS

FAISS is the reference ANN library (Meta). Index types:

  • IndexFlatL2 / IndexFlatIP: exact brute-force, no approximation. Use for < 1M vectors or as ground truth for recall benchmarking.
  • IndexIVFFlat: inverted file index. nlist = number of Voronoi cells (rule of thumb: sqrt(N) to 4*sqrt(N)). At query time, nprobe cells searched — trade recall for speed. Requires training: index.train(vectors).
  • IndexIVFPQ: adds Product Quantization compression. m subquantizers (must divide d), nbits=8 standard. Dramatic memory reduction (32x with m=d/4, nbits=8) at modest recall cost.
  • IndexHNSWFlat: HNSW graph index. M = edges per node (16-64, higher = better recall + more memory), efConstruction = search width during build (200-500). At query time: index.hnsw.efSearch (32-256). No training required.
  • IndexIVFPQ + HNSW coarse quantizer: best recall/memory/latency for large-scale production.

Read the full file on GitHub · 102 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 1mo ago First seen · 102 lines · 71 tokens per session scan A 8609dc67ca0a

Subscribe to this mod's changes

vector-databases is a skill published in the GitHub repository LuuOW/meridian-mcp (0 stars, last pushed 6d ago), licensed MIT. It adds 71 tokens to every session and 2,659 once invoked, about $0.0003 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.

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