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

Annotations already declare readOnly/idempotent/non-destructive, so the safety profile is covered. The description usefully adds that no API key is required and that there is a rate limit (max 20 queries/session), which is real behavioral context beyond the annotations. It muddies this by pairing 'Price 0.01 USDC/query' with 'FREE preview — no key, no payment', leaving the actual cost model ambiguous.

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 text repeats the same message three times ('No API key needed', 'FREE preview — no key, no payment', 'Try ... now'), and front-loads a marketing CTA rather than the tool's function. Informational content (rate limit, sample questions) is buried inside promotional phrasing.

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 a zero-required-parameter, read-only preview with a fully documented schema and no output schema, the essentials are present. But the description is cluttered with listing-specific sales copy and an ambiguous price statement, so it is adequate rather than complete or clean.

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 100%, so both parameters (slug, question) are already documented, including the echo-back behavior of `question` and the slug defaulting to the routed listing. The description adds nothing about parameter syntax or defaults. Baseline 3 is appropriate when the schema carries the parameter documentation.

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 states that this is a free, guest-callable preview of a data listing, which matches the tool name and the schema's own summary ('Free, guest-callable taste of a listing'). However it never distinguishes this from the many session/query siblings (data_session_query, data_session_open), so an agent still has to infer the boundary. The purpose is clear but lacks sibling differentiation.

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?

There is implicit usage guidance ('call this now', 'Try one of the sample questions now') and a soft signal that payment is not needed, which implies 'use this before paying for a session'. But there is no explicit when-to-use vs data_session_query, no stated prerequisites, and no exclusion conditions beyond the pricing note. Usage is only implied.

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