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grafeo-mcp

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by GrafeoDB

create_vector_index

Set up an HNSW vector index for fast similarity search on graph nodes. Requires label, property, dimensions, and metric to index existing and future vectors.

Instructions

Create an HNSW vector index for fast similarity search.

Call this once before using vector_search on a label + property pair. If nodes with the given label already have vector values in the property, they are indexed immediately; future nodes are indexed on insertion.

Args: label: Node label to index (e.g. "Document"). property: Property containing embedding vectors (e.g. "embedding"). dimensions: Vector dimensionality (e.g. 1536 for OpenAI, 384 for MiniLM). If None the engine infers it from existing data. metric: Distance metric — "cosine" (default), "euclidean", "dot_product", or "manhattan". m: HNSW links per node (default 16 inside the engine). Higher values give better recall but use more memory. ef_construction: HNSW construction beam width (default 128 inside the engine). Higher values build a higher-quality index but take longer.

Returns: Confirmation string on success, or an error message.

Example call: create_vector_index("Document", "embedding", 1536, "cosine", m=32, ef_construction=200)

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
labelYes
propertyYes
dimensionsNo
metricNocosine
mNo
ef_constructionNo

Output Schema

TableJSON Schema
NameRequiredDescriptionDefault
resultYes
Behavior4/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

No annotations are provided, so the description carries full burden. It discloses indexing behavior for existing and future nodes, parameter effects, and return type. It could mention idempotency or side effects, but overall good transparency.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is well-structured: purpose, usage, parameter list, returns, example. Every sentence adds value, and it is concise without being terse.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the complexity (6 params, no annotations), the description is fairly complete. It includes an example call. It could elaborate on error cases or performance, but overall sufficient.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters5/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 0%, but the description explains every parameter with examples, defaults, and effects (e.g., '15 for OpenAI' for dimensions). This adds significant meaning beyond the schema.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the tool creates an HNSW vector index for fast similarity search. It specifies the usage context (call once before vector_search on a label+property pair) and distinguishes it from siblings like create_text_index and vector_search.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description explicitly advises calling this once before using vector_search. It provides clear context but does not explicitly mention when not to use or alternatives. The usage context is effective for an AI agent.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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