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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so safety is covered. The description adds genuinely non-structured behavior: the content mirrors the website FAQ wording (static reference text, not live data) and should be consulted a single time, which tells the agent this is a one-shot orientation read rather than a repeated data query.

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?

Two short sentences: the first front-loads the content scope, the second delivers the actionable instruction. No filler and no redundancy with structured fields.

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?

With no parameters and no output schema, the description's job is to convey what the caller receives and why — it states the covered topics and, via the FAQ wording note, signals prose documentation rather than structured data. Nothing needed to call this tool correctly is missing.

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?

The tool takes zero parameters and the schema is trivially complete, so there is nothing to document beyond the baseline. The description correctly spends no words on parameters.

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 the resource (the Zensei Index) and enumerates what the content covers: what it is, how to read the score, how it is built, and what the server serves. It is clearly the documentation/FAQ tool and thus distinguishable in role from data-bearing siblings like zensei_index_summary or zensei_index_today, though no sibling is named explicitly.

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?

It gives an explicit usage instruction — 'Call it once before interpreting any score' — which establishes both timing (before interpreting scores) and call frequency. It stops short of naming when-not-to-use or pointing to an alternative sibling, so it is not a full 5.

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