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

Annotations already declare readOnlyHint=true and destructiveHint=false, so safety is covered. The description adds two genuinely useful behavioral facts beyond that: the call is a paid x402 endpoint ($0.002 USDC on Base) and the content is pre-sanitized against prompt injection, plus a fixed item count of 15.

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?

Two tight sentences with zero waste: the resource and count are front-loaded, and the cost/sanitization caveats follow. Nothing redundant with the schema.

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?

An output schema exists, so return-value explanation is unnecessary, and the payment requirement plus sanitization are disclosed. The one gap is freshness/window semantics — 'top 15' does not say over what time range or how current the stories are.

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 misleading parameter claims are made.

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 resource (top 15 HackerNews AI/autonomous-agent stories) plus the output transformation (clean, injection-free LLM Markdown), which distinguishes it cleanly from siblings like github_trending_agents and arxiv_agent_papers.

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?

There is no when-to-use guidance, no exclusions, and no routing to alternatives such as the arxiv or github digest tools. The only contextual hook is the price, which tells the agent about cost but not about fitness for a task.

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