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

Annotations already provide readOnlyHint, idempotentHint, and destructiveHint. The description adds useful context beyond annotations: results are live and updated every few minutes, no authentication is required, and it explicitly lists the fields returned. This enriches agent understanding without contradicting structured metadata.

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?

Four sentences, all substantive. The purpose is front-loaded, followed by ranking behavior, freshness, auth requirements, and licensing. No filler or redundancy; each sentence earns its place.

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 simple read-only tool with one optional parameter and an output schema, the description covers everything an agent needs: return fields, count cap, ranking logic, live-update behavior, and access constraints. No critical information 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?

The input schema fully documents the single 'limit' parameter, including range and default. The description mentions 'up to 20 posts' but adds no new semantics beyond the schema's existing maximum. Since schema coverage is 100%, the baseline of 3 applies.

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?

Description clearly states it fetches current top stories from Hacker News, specifies return fields (title, URL, score, author, comment count, submission time), and distinguishes from sibling tools by mentioning the front-page ranking algorithm. Agents can confidently select this over stories.best or stories.new.

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?

Provides clear context—this returns the live top stories as ranked by HN's score/recency algorithm—but does not explicitly mention alternatives for other story categories (best, new). The usage is implied by the name and description, but without exclusions, it falls short of a full 5.

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