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

Annotations already declare readOnly, idempotent, non-destructive, closed-world. The description adds the return payload shape ({"message", "how", "free_tier"}) and, importantly, an error contract: it never raises a protocol error but returns an {"error": ...} object, and retries after correction are safe. Only rate limits/volume considerations are absent.

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?

Front-loads what it does and that it is free, then usage, then output, then error behavior — a sensible order. The error/retry sentence is somewhat verbose for a zero-argument informational tool, but each sentence carries distinct information.

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?

An output schema exists and annotations cover the safety profile, so the description need not restate return values beyond a brief shape hint. Between purpose, triggers, exclusions, and the error contract, an agent has everything needed to call it correctly.

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?

Zero parameters, so the baseline is 4. The description confirms 'Takes no arguments', which matches the empty schema with additionalProperties: false, but adds no further parameter meaning to give.

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?

States a specific verb and resource: explains how to unlock full personas, paid skills, and kits, and explicitly notes the FREE tier. It also names the siblings it is not for (list_kits, preview_product) for per-bundle/per-product pricing, so an agent can separate it from catalog tools without opening a schema.

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?

Gives concrete triggers: when a premium tool has been refused, or the caller asks what a plan covers. It also gives an explicit exclusion (pricing questions belong to list_kits/preview_product), leaving nothing to inference.

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