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

Annotations already declare readOnlyHint, openWorldHint, and idempotentHint, so the safety and idempotency profile is covered. The description adds the freshness guarantee ('right now') and the returned fields, which is useful context, but omits anything about rate limits, caching/refresh cadence, or how the ranking is determined. With annotations doing the heavy lifting, a 3 is appropriate.

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 short sentences, front-loaded with the resource and scope, with no redundant restatement of the title. The closing 'Try GET /news/sample.' is cryptic and arguably wastes a line, since an MCP agent has no defined way to invoke an HTTP GET, which keeps this from a 5.

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?

This is a simple read-only tool with zero required parameters, full schema coverage, and an output schema that already documents the return shape, so the description needn't explain return values. It covers resource, freshness, and payload fields adequately. The only shortfall is the unexplained sample-endpoint pointer, which could mislead a caller.

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% and the single `limit` parameter is fully documented in the schema (range 1-25, default 10). The description adds no syntax or behavior detail about the parameter beyond what the schema already states, so 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?

The description names a specific resource and scope: 'Top Hacker News headlines right now', plus the returned fields (title, URL, score, comments). An agent can immediately tell this apart from siblings like weather, crypto, or search. It stops short of explicitly differentiating from a generic search tool, but the resource is concrete and unambiguous.

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?

'Fresh links for agents that need current tech/startup signal' implies the use case, which is more than nothing, but it offers no when-not-to-use guidance and never names an alternative (e.g., search or read_web_page for a specific topic or URL). The trailing 'Try GET /news/sample.' is not actionable guidance for an MCP caller.

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