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

With no annotations, the description carries the full burden and does disclose two things that materially affect invocation: comments are top-level only and capped at 30, text is truncated to 500 characters, and each call costs $0.002 USDC via x402 on Base. What it omits is failure behavior for an invalid id and whether truncated content or pagination is available beyond the stated caps.

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 sentences with zero waste: the identity and payload come first, the cost and payment rail second. Nothing is repeated from the title or 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?

For a two-parameter read tool with no output schema and no annotations, the description covers return shape, truncation limits, and payment requirements, which is most of what an agent needs. Missing only edge-case behavior such as invalid ids or requesting more than 30 comments.

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 coverage is 100%, so both parameters are already documented, and the description adds little beyond echoing the 30-comment cap. It does not clarify the string-typed maxComments despite it being a numeric range, nor what happens if maxComments exceeds 30.

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 and resource: fetch one Hacker News story or comment by id, with an enumerated set of returned fields (author, time, text, reply count) and an explicit comment cap. It is clearly distinguishable from hn_user and a listing-style hn_hackernews, but it never names those siblings to route the agent explicitly.

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?

Usage is only implied: you supply an id and get a single item back, so the case for calling it is fairly self-evident. There is no explicit when-to-use/when-not or pointer to hn_hackernews for browsing or hn_user for author lookups, so the agent must infer which of the three HN tools applies.

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