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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint false, covering the safety profile. The description adds genuinely useful behavioral context beyond annotations: no API key required, pricing of 0.01 USDC/query, a session cap of 20 queries, and the specific listing targeted. This helps the agent understand cost and rate limits before invoking.

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 important call-to-action and includes essential pricing and listing details. However, it repeats the 'no key/free/no payment' point multiple times and uses promotional phrasing like 'call this now' and 'Try one of the sample questions now,' which adds redundancy without new 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?

For a simple read-only preview tool with two optional parameters and no output schema, the description covers the key operational facts: what listing is being previewed, that it is free and guest-callable, the cost for paid queries, and the session limit. Minor gaps like expected return format are mitigated by the schema's 'public metadata only' note and the annotations' safety profile.

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 slug and question. The description adds value by giving concrete sample questions that illustrate how the question parameter is used, and by naming the listing 'biopreprintwatch,' which clarifies the slug's real-world referent.

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 makes the tool's purpose explicit: it is a free preview of a specific data listing ('biopreprintwatch: New Life-Science Preprints') with sample questions and no API key required. It clearly distinguishes itself from paid or session-based sibling tools by emphasizing 'FREE preview — no key, no payment.'

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 gives clear actionable context: 'No API key needed — call this now' and 'Try one of the sample questions now,' indicating this is the entry-point tool for trying a listing before paying. However, it does not explicitly name alternative tools like data_session_query or data_session_open as the paid path, so exclusions are only implied.

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