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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint=false. The description adds useful behavioral context beyond annotations: it is free, returns JSON, and includes exact payment terms (USDC on Solana mainnet or Base, payTo per network, facilitator).

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 'Free. Start here' and packs essential details into two dense sentences. It is slightly long but each clause contributes substantive information about the catalog's contents and limitations.

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 parameters and no output schema, the description must explain return content, and it does: every tool with price, required arguments, return value, x402 payment terms, and label semantics URL. It also clarifies scope by noting it carries no market data, leaving no obvious gap for an agent choosing among siblings.

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?

This tool has zero parameters, so the schema carries no burden and there is little to add. The rubric grants a baseline of 4 for zero-parameter tools, and the description appropriately focuses on what the catalog contains rather than parameters.

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 states a clear, specific purpose: it catalogs every tool with pricing, required arguments, return contents, x402 payment terms, and label semantics URL. It also distinguishes itself from market-data siblings by explicitly noting it 'carries no market data.'

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?

It gives explicit usage guidance: 'Start here' and 'Use it first to choose a tool and budget.' It also provides a clear exclusion ('carries no market data'), helping the agent avoid this tool when market data is needed.

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