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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint, so the safety profile is covered. The description adds useful behavioral context: no API key required, free preview, a per-query price for the underlying listing, and a query-per-session limit. It does not contradict the annotations, though the mention of 'Price 0.01 USDC/query' could briefly confuse an agent into thinking this tool itself is paid.

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 the most urgent call to action ('No API key needed — call this now') and includes valuable sample questions. However, it repeats the free/no-key/no-payment message multiple times, and the promotional emoji-laden tone adds noise without adding informational value.

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 simple tool with only two optional parameters, the description covers key operational facts like pricing, session limits, and example questions. It does not explain what the tool returns, and with no output schema the agent is left to infer the response shape; the schema's note that the question is 'echoed back' is also not surfaced in the description.

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 the schema already documents both slug and question well. The description adds concrete sample questions that map directly to the question parameter, and it names the current listing slug (showhnwatch), giving practical examples an agent can use immediately.

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 identifies the tool as a free preview for the showhnwatch listing and includes sample questions, making the core purpose clear. However, it never explicitly states 'preview this data listing' in plain terms, relying on the phrase 'FREE preview' and the annotation title. It does not differentiate itself from siblings like data_session_query beyond implying free access.

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 description strongly implies the tool is for trying a listing without an API key or payment, saying 'No API key needed — call this now' and 'FREE preview — no key, no payment.' It does not explicitly say when not to use it or mention alternatives such as data_session_query or data_session_open, leaving the routing decision mostly implicit.

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