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

With no annotations, the description carries the full burden and does well: it discloses that no API key/account is needed, that nothing is downloaded, and that each call costs $0.005 paid via x402 (USDC) — material behavioral facts for a paid tool. It omits rate limits and error/timeout behavior, but the cost and auth profile are unusually well covered.

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 function and return fields, then usage context, then auth and pricing — a sensible ordering with no filler. The long enumeration of return fields makes it slightly dense, but every clause contributes information.

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?

With no output schema and no annotations, the description compensates by enumerating the returned data (status, redirect chain, final URL, HTTPS, content type/size, security headers) and the commercial/auth model. An agent has everything needed to decide and invoke 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 100%, so both the url and method parameters are already fully documented in the schema. The description adds no syntax or format detail beyond that, so the baseline of 3 is appropriate — the schema does the semantic heavy lifting here.

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 ('Checks one URL') and enumerates exactly what it returns: HTTP status, hop-by-hop redirect chain with codes, final URL, HTTPS termination, content type/size, and security headers. The clause 'without downloading the page' implicitly distinguishes it from the sibling web_read, so an agent can select between them without opening a 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?

'Built for going through a list of links one at a time' gives concrete usage context, and 'without downloading the page' signals when to prefer this over a content-fetching tool. It stops short of explicitly naming web_read as the alternative or stating when NOT to use it, so it lands just below the top tier.

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