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

Annotations only declare readOnlyHint and openWorldHint; the description adds the critical behavior an agent cannot infer — the operation is paid, and calling it does NOT return data but instead returns the HTTP request plus x402 payment requirements that must be settled with an external x402 client. This two-step, cost-bearing flow is essential and well disclosed.

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 tight sentences with the most decision-relevant fact (Paid, $7 USDC via x402) front-loaded, followed by scope, licensing/attribution, and the payment mechanics. No filler or repetition.

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 input parameters and no output schema, the description carries the return-value burden and does so by explaining that the immediate response is an HTTP request plus payment requirements rather than the dataset itself. It covers scope, cost, licensing, and delivery, leaving only minor details (e.g. response payload size, format of the payment challenge) unstated.

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 4 applies; no parameter-level explanation is needed or missing.

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 ('Full dump: Agent Tool Directory') and quantifies scope (~13,000 MCP servers + x402 APIs in one unified JSON schema). This clearly distinguishes it from the split siblings dump_mcp_servers and dump_x402_services as the combined superset.

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 strong usage context by flagging the tool as paid ($7 USDC via x402) and explaining the two-step pay-to-fetch flow, which governs whether an agent should call it at all. It never explicitly names an alternative (e.g. the free sample or split dumps) or states when-not to use it, so it stops short of full routing guidance.

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