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

With no annotations, the description does carry useful behavioral weight: collection start date, 10-minute refresh cadence, and especially the paid model ($0.005 USDC on Base, 402 challenge on unpaid calls) — critical for an agent to know. However, it also advertises parameters ('hours up to 720, limit up to 200') that do not exist in the schema, which actively misleads about how the call behaves.

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, front-loaded with the resource, and the pricing/freshness clauses earn their place. But the parenthetical parameter list is wasted space — it describes options this tool does not accept.

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 single-param tool with no annotations and no output schema, the description must explain what 'url' means and what comes back (a ranked list? endpoint records?). It does neither, and the pay-per-call disclosure, while valuable, does not substitute for that missing core.

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 only real parameter is 'url', and the description never mentions it, nor does the schema description ('required') add meaning. Worse, the description names two parameters (hours, limit) that are absent from the schema, so the parameter picture it paints is wrong rather than merely thin.

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?

It states a resource ('Newest paid x402 endpoints indexed by the census') with a recency qualifier, which loosely sets it apart from census_search and census_stats, but the verb is missing and 'x402 endpoints' / 'the census' are unexplained jargon. An agent can guess this lists recently-seen pay-per-call APIs, but not confidently.

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?

No when-to-use versus when-not, and no explicit contrast with the four sibling census_* tools. Recency ordering is only implied by the word 'Newest', leaving the agent to infer selection criteria on its own.

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