List paid endpoints

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

Annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, so the safety profile is covered; the description still adds the auth detail 'no account' and the return shape. It largely restates read-only rather than adding new behavior beyond that, so it sits just below the top.

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?

Three sentences, zero waste, front-loaded with the what, then the when, then the return shape. Nothing redundant except a brief restatement of read-only that is harmless.

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, the description compensates by describing the JSON envelope ('endpoints[]' with resource URL, price, asset, network and price history). For a simple filtered-list tool with full annotation coverage, nothing an agent needs to call it 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?

Schema description coverage is 100%, so limit, maxUsd and origin are already fully documented in the schema. The description adds no parameter syntax or filtering nuance beyond that, which is the correct baseline when the schema does the heavy lifting.

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 ('Lists x402-priced endpoints') plus the exact data surfaced ('price per call the hub read from their own 402 answers, and how that price moved over time'). It explicitly separates itself from the sibling search_agents, so an agent can route without opening either 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?

Names the concrete use cases ('compare what a capability costs across providers or to find the cheapest') and names the alternative tool plus the condition that selects it ('search_agents is better for finding a capability by what it does'). Explicit when-to-use and when-to-use-something-else.

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