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

With zero annotations the description carries the full burden, and it does substantial work: discloses cost ($0.01/call), the payment rail (USDC on Base, eip155:8453), the exact payment field params._meta["x402/payment"], a free /demo and /quickstart, and the HTTP endpoint. Gaps remain on result-count limits, rate limiting, and failure modes for an unpaid call.

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-loaded with the core value proposition and densely packed with operational detail in four sentences. It loses a point for repeating the price twice ("in one $0.01 call" then "Price: $0.01 per call") and for placing the raw HTTP URL in a paragraph whose audience is already an MCP client.

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 4-parameter, no-annotation, no-output-schema tool, the description covers cost, payment mechanics, input modes, and data sources — enough to invoke it correctly and know it will be billed. It does not describe the shape of the returned result set (how many ranked results, whether markdown is interleaved with rankings), which an agent must discover at runtime.

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 baseline is 3 regardless. The description reinforces the q=/url= mutual-exclusivity semantics but adds nothing about chars= truncation behavior or extract= (0-4) that the schema does not already state.

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 composite verb and resource: ranked search results from four named sources plus page-to-markdown extraction in a single call. The dual-mode nature (q= search vs url= extract) is immediately clear. It stops short of 5 because nothing in the text distinguishes it from the sibling websearch__brief or web_extract__extract — the 'briefbatch' suffix is never explained relative to 'brief'.

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?

"Pass q= to search, or url= to extract any single page" does give mode-selection guidance, but it is framed as invocation syntax rather than when-to-use. There is no mention of when an agent should pick this over websearch__brief, web_extract__extract, or webmd__extract, and no stated exclusions or prerequisites beyond the paywall note.

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