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

With readOnlyHint and openWorldHint already covering the safety profile, the description still adds substantial non-obvious behavior: it is deterministic ('No AI involved'), a dead link is a valid non-failure result, a request with no usable URL is not charged, and the call costs $0.01 USDC via x402. Billing and failure semantics are 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 tight sentences lead with the resource and outputs, then usage, then behavior and pricing. Nothing is padded, though the billing sentence is dense enough that it slightly blurs the front-loaded structure.

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, so the description takes on the burden of describing return values, and it does so explicitly (status, redirect endpoint, title, soft-404 warning). Combined with the cost and failure-handling rules, an agent has everything needed to call it 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 coverage is 100% for the single 'urls' parameter, so the baseline is 3. The description goes slightly beyond the schema by restating the 1-10 cardinality and adding the charge rule tied to usability of the supplied URL, which clarifies what counts as a valid input.

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?

The description names a specific verb and resource ('Checks 1-10 URLs') and enumerates exactly what is returned: HTTP status, redirect destination, page title, and a soft-404 warning. That enumeration distinguishes it from siblings like check_doi, page_text, and robots_check without the agent needing to open another 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?

'Use it to catch dead or made-up citations' gives a clear use context, and the citation framing separates it from the DOI/quote checkers. However, it never states when NOT to use it or names a sibling alternative for a related task (e.g. check_doi for DOIs), so it stops short of a 5.

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