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

With no annotations supplied, the description carries the full behavioral burden and does so well: it discloses automatic chunking, per-key collections, a 50,000-chunk ceiling, upsert billing per 5 chunks, a €0.001 per-query charge, and that billing routes through the 'Authorization: Bearer' key. That is substantial cost and quota context an agent could not otherwise know. It falls short of 5 because it does not state whether delete is permanent or what happens on an unknown op.

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

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

The description is front-loaded with purpose, limits, and cost before the parameter glossary, which is the right ordering. It is dense and slightly run-on, but every clause carries information and nothing is padding.

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

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

For an eight-parameter multi-operation tool, the description covers what the tool is, the operations, the quotas, the billing model, and the auth mechanism. Return values are covered by the existing output schema, so no further explanation of results is required. An agent has enough to call this correctly on a first attempt.

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

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

Schema description coverage is 0%, so the description must compensate entirely, and it does: every one of the eight parameters is explained, including op values with the default, collection name and its 'default' default, top_k range 1–50 with default 5, the docs JSON shape [{id, text, meta}], and ids as comma-separated. This is meaning the schema itself does not convey at all.

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

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

The description names a specific resource and its verbs: 'Your own vector index behind the API key: upsert documents (chunked automatically), query in any language, get ranked chunks with metadata.' That is far more than a restatement of the name. It stops short of a 5 because it never distinguishes this from nearby siblings such as embed, memory, or web_search, so an agent must infer the boundary itself.

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

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

The op enumeration ('query (default) | upsert | delete | list') gives real operational routing, and the default makes the common path obvious. However, there is no guidance on when to choose this tool over embed or memory, and no stated preconditions for the mutating ops. Usage is implied by the parameter list rather than spelled out.

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