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

Annotations already declare readOnlyHint=true and openWorldHint=false, so safety is covered. The description adds genuinely new behavioral context beyond that: the call is free, returns only a few sample rows (not full data), emits JSON, and discloses the pricing tiers for the paid siblings ($0.01–$4.99). It omits pagination/result-size limits, which is a minor gap.

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-loaded with the two most decision-relevant facts (FREE, Use first), followed by one dense sentence. The parenthetical pricing inventory is somewhat run-on, but every element (field list, sample-row caveat, output format) earns its place for a discovery tool.

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?

With no output schema and no parameters, the description carries the full burden and discharges it: it enumerates the return fields, notes that only sample rows are included, gives the output format, and explains the cost structure that motivates the downstream siblings. Nothing an agent needs to call this correctly is missing.

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?

The tool takes zero parameters, so the baseline is 4. The description correctly implies no filtering inputs are needed and instead spends its budget on return-field semantics, which is the right trade-off.

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 (list) and resource (every dataset for sale), then enumerates the exact returned fields (id, title, category, row count, field names, created_at, sample rows, USDC price). Combined with 'Use first', an agent can place it ahead of buy_dataset/preview_dataset without opening any 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?

'FREE. Use first.' gives clear, actionable context that this is the entry-point call before the paid siblings. It stops short of naming buy_dataset/preview_dataset or stating when NOT to use it, but the intended ordering is unambiguous.

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