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

Annotations already declare readOnly, idempotent, non-destructive, and non-open-world, so the bar is lower. The description still adds genuinely beyond them: 'No purchase or wallet action occurs' rules out crypto-side effects the annotations cannot express, and 'Results are catalog entries, not proof of demand' pre-empts over-interpretation of the returned data. It stops short of describing result shape/pagination, so not a 5.

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 read-only/free/catalog purpose, then routing guidance, then safety caveats — a logical order. Four sentences are dense but each carries information; the embedded price ranges for the sibling add slight bulk without much selection 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?

With zero parameters, no output schema, and rich annotations, the definition supplies everything needed to call it correctly: scope, no-side-effect confirmation, result interpretation caveat, and sibling routing. No meaningful gap remains for a parameterless list operation.

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, which sets the baseline at 4. The description reinforces this with the explicit call signature 'Use list_products with {}', confirming no arguments are needed, though it cannot add semantic depth beyond that.

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+resource: a read-only, free catalog of priced x402 tools, and enumerates the covered categories (JSON/security, funding rates, extraction, seller-payment analysis, agent operations). It clearly distinguishes itself from list_premium_agent_packs and get_purchase_instructions. The only friction is the slightly tension-filled framing of a 'free catalog' of 'priced' tools and the jargon 'exact priced x402', which adds a beat of ambiguity.

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?

Explicitly tells the agent how to call it ('with {}'), what this tool covers ('ordinary APIs'), and names the alternatives for adjacent cases: list_premium_agent_packs for $99.90–$2,499.90 credit packs and get_purchase_instructions for a known product. This is textbook when-to-use/when-not guidance naming the sibling tools.

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