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 adds genuinely new behavioral context the annotations lack: the call is free, requires no payment, and should be made first as a discovery step before paid tools.

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?

A single front-loaded sentence ('Free, call first') followed by the payload contents and the routing condition. Every clause carries information — no restatement of the name or title and no filler.

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-parameter, read-only discovery tool with no output schema, the description still enumerates what comes back (price, paid URL, teaser, payTo) and when to reach for it. An agent has everything it needs to call it correctly on the first turn.

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 there is nothing for the description to disambiguate; baseline for a no-param schema is 4. The description does clarify that the returned SKU entries carry price, paid URL, teaser and payTo, which is return-shape information rather than parameter guidance.

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 and resource ('list every SKU with price (Base USDC), paid URL, free teaser and payTo') and explicitly frames the outcome ('so you can pick the right paid tool'). That framing distinguishes it from the 20+ sibling tools, which are all single-purpose actions rather than a catalog.

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?

Gives a clear entry condition ('Use when unsure which tool fits') and a priority ordering ('Free, call first'), which is exactly the routing guidance an agent needs. It stops short of naming when not to call it, but the condition is unambiguous.

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