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

Annotations already cover the read-only, non-destructive, open-world profile, so the bar is lower; the description goes beyond them with material operational facts: a per-call price of $0.005 USDC, x402 payment handled inside the call, supported chains, and automatic payment for x402 MCP clients. It omits failure-mode behavior (timeouts, redirect loops, unreachable hosts), which would round it out.

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 the purpose, then usage, then parameters, then payment details. Every clause carries information, though the pricing/x402 sentence plus the free-sample example makes it longer than strictly needed for tool selection.

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, and the description compensates by listing exactly what comes back. With annotations covering safety and pricing covered in prose, an agent has everything required to select and invoke the tool correctly.

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 50%, so the description has to compensate, and it does name both parameters: url as required and method as GET-by-default with HEAD as the alternative. It adds no format or timeout guidance, but the gap for a two-parameter tool is minor.

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 (check a URL's reachability) and enumerates the exact return payload: final status code, redirect chain, response time, content-type, server header, content length. This clearly separates it from siblings like screenshot, web_scrape and ssl_check without the agent needing to open any 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?

Names concrete use cases (link validation, uptime checks, canonical URL resolution) and explicitly routes the agent to use it before spending money on a scrape/screenshot, which implicitly positions it against those siblings. It stops short of stating exclusions, e.g. that it does not follow login walls or extract page content.

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