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 by structured data. The description adds genuinely useful behavior context — no API key required and a 20-query-per-session cap — but never explains what the preview actually returns or how it differs in content from a paid query, and the price line (0.01 USDC/query) sits awkwardly next to 'FREE'.

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 is dominated by promotional framing: a checkmark emoji, a price line, two long sample questions, and a redundant restatement of the no-key point ('No API key needed' followed by 'FREE preview — no key, no payment'). The actual purpose appears only as a fragment, so the description is front-loaded with sales copy rather than function.

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 two-optional-parameter read tool with full schema coverage and rich annotations, the basics are present: what listing, that it is free, and the quota. What is missing is what a preview response contains and whether a slug is needed when not routed via the session URL, which matters given there is no output schema.

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% and neither of the two optional parameters is discussed in the description; the slug and question semantics live entirely in the schema. Baseline 3 applies since the description neither compensates nor adds meaning.

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 does name the resource (usnwatch: Ubuntu Security Notices) and frames itself as a free preview, so an agent can infer it returns public sample metadata for one listing. However, the operative statement of purpose is buried under marketing copy and sample questions, and it never explicitly contrasts itself with data_session_query, the obvious paid counterpart.

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 a soft call to action ('Try one of the sample questions now') and a quota hint ('max 20 queries/session'), but no explicit statement of when to use this tool versus data_session_query or data_session_open. The agent is left to infer that preview precedes paying.

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