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

The annotations already declare readOnly, idempotent, openWorld, and non-destructive, so the safety profile is covered. The description adds genuinely non-structured behavior: the tool costs $0.004 USDC on Base and requires an X-PAYMENT header, which is critical for an agent to know before calling. It stops short of explaining what happens on a 402 / missing-payment response, which would have made this a 5.

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 paid/x402 nature and the price before any parameter detail. Every sentence carries information, though the enumeration of freshness values and the num cap duplicates the schema verbatim and could have been spent on the q/query ambiguity instead.

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?

There is no output schema, so the description is the only place result shape could be explained, yet it says nothing about what a successful response contains (articles, fields, count) or what a 402 challenge looks like. Combined with 9 largely undocumented parameters, a duplicated query slot (q vs query), and no gl/hl locale explanation, an agent has meaningful gaps to guess through.

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 only 22% across 9 parameters, so the description must compensate, and it partially does — freshness, dateFrom/dateTo, page, and num are called out. However, it mostly restates constraints already encoded in the schema (the freshness enum and the num<=100 maximum) rather than adding meaning, and it leaves the most dangerous ambiguity untouched: the schema exposes both "q" and "query" as separate string parameters with no hint as to which one the search actually uses.

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 verb and resource ("News search") plus the transport/payment mechanism (x402). It is clear what the tool does, but it never distinguishes itself from plausible siblings such as news_digest, web_search, or scholar_search, so an agent cannot tell from this text alone why it would pick news_search over news_digest.

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?

The only usage instruction is mechanical — "Pass an x402 payment in the X-PAYMENT header" — which is a prerequisite rather than guidance on when to use this tool. There is no statement of when to prefer it over the 18 siblings, and no note about when a paid news search is or isn't warranted versus the free web_search or the summarization-oriented news_digest.

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