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

Annotations already declare readOnly/openWorld/non-destructive, and the description adds genuinely new behavioral facts: an x402 payment is required per call, and there is no charge when the search fails or returns nothing. That billing/refund semantics is exactly the kind of context annotations cannot convey.

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 dense sentences, front-loaded with what it does and the return shape, then routing, then query/date guidance, then billing. Nothing is padded or repeated.

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?

Output schema exists, so return values need not be explained, yet the description still gives the shape; it also covers routing, date filtering, cost, and no-charge-on-failure. Nothing an agent needs to invoke this correctly 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?

Schema description coverage is 100%, so the schema already documents n, q, since and until; baseline would be 3. The description adds value beyond it by telling the agent that plain phrases work as well as keywords and that since/until filter on publish date (useful for news queries).

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?

Specific verb+resource ("Runs a web search") plus the exact return shape {query, results:[{title,url,snippet}]}. It explicitly distinguishes itself from research.answer, so an agent can choose between the two without opening either schema.

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?

States when to use it ("raw links to read yourself") and names the alternative with the condition that selects it ("use research.answer for a written answer"). It also adds a topical-use hint: since/until "suits recent news".

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