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

Goes well beyond the readOnly/openWorld annotations: discloses output shape (title, snippet, linked URL, author, points, comments, up to 5 top comments), summary fields, failure semantics ('a source that is down reports an error without failing the call'), pricing ($0.006 USDC, x402, pay-automatic), and the free-sample path. With no output schema, this carries the full burden and does so thoroughly.

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?

Front-loads purpose then output shape, then a dense parenthetical of param defaults and pricing. Mostly earns its sentences, but the pricing/x402/sample block is long and could be tightened; the parenthetical param list duplicates schema defaults somewhat.

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 7-param, multi-source read tool with no output schema and an open-world, additional-payment profile, the description supplies output structure, partial-failure behavior, cost model, and a worked example. An agent can decide whether to call and invoke it correctly without opening the schema for most decisions.

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 only 43%, so description must compensate – and it does for most params (query-or-url requirement, sources default/list, sort default, days range 1-3650, limit 1-20 default 5, comments 0-5 default 2). It explicitly states query/url are 'one required.' Minor gap: sources values and enum semantics are left entirely to the schema, and the mutual-exclusivity of query vs url could be stated more firmly.

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 ('Find out what people say about a topic or link'), names the exact sources (HN, Bluesky, Lemmy), and explicitly distinguishes itself from absent siblings like news_search and web_search by naming what is NOT included (Reddit and X). The URL-based 'find every thread that shared that link' use case is concrete and agent-recognizable.

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?

Explicit when-to-use guidance is embedded throughout – 'useful for product launches, articles and competitors' for the URL mode, plus a clear exclusion of Reddit and X. The free sample input is a practical usage pointer. The alternative-vs-sibling routing is implied by the source scoping rather than by naming a sibling, but it is unambiguous.

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