web_search

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

Annotations already cover read-only/idempotent/open-world safety, but the description adds material context the annotations cannot: per-search pricing via x402 (USDC on Base) or an API key, and that an HTTP 402 response carrying a decoded price is a quote, not a failure. That payment edge case is precisely the kind of behavior an agent would otherwise misread as an error.

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 short blocks (summary, example, when-to-use, behavior) with the core capability front-loaded and no filler sentences. The pricing paragraph is the longest but every clause carries operational meaning.

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?

No output schema exists, yet the description enumerates the returned fields and covers the payment path and the 402 edge case. For a 4-param, single-required read tool, an agent has everything needed to call it and interpret the response.

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 the baseline would be 3; the description earns extra by supplying a concrete example URL that shows parameter formatting and the interaction of q, max_results and topic. It does not restate defaults or the 400-character limit, so it stops short of a 5.

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 ('Real-time web search') plus the exact return shape (title, URL, snippet, score, optional synthesized answer). It explicitly distinguishes itself from the sibling sanity_check, so an agent can route 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?

Gives an explicit when ('agent needs fresh web results with titles, URLs and snippets'), an explicit when-not ('Not for verifying a claim'), and names the alternative with the exact mode to use ('use sanity_check with mode open').

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