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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is known. The description adds genuinely non-obvious behavior beyond that: a 64 KB input ceiling, an explicit 'nothing stored' data-handling guarantee, a $0.005 USDC per-call price, and the full x402 payment handshake including the params._meta["x402/payment"] fallback. It stops short of covering rate limits, what happens on partial detection failure, or error shapes.

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?

The text is front-loaded and dense with no filler: transport and size limit first, then detection coverage, then return shape, then storage, cost, and payment mechanics. The final payment sentence is a long run-on that bundles three distinct facts, but every sentence carries information an agent needs.

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, the description correctly carries the return-value burden by stating it returns redacted text, per-type counts, and findings with offsets. Payment and pricing are fully covered. The main gap is behavioral detail for the two undocumented optional parameters, which matters given a 33% schema coverage on a three-parameter tool.

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 only 33%: `text` is documented in the schema, but `style` (enum label/mask) and `types` (array of strings) carry no descriptions anywhere. The description partially compensates for `types` by enumerating the detectable PII categories an agent could filter on, but it never explains what `label` versus `mask` output looks like or what the default style is, leaving the enum's meaning unresolved.

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 opens with a specific verb and resource ("POST text") and enumerates exactly what is detected and redacted, including detection methods like Luhn validation, IBAN mod 97, and IPv4/IPv6. That level of specificity lets an agent distinguish it from nearby siblings such as extract_contacts or injection_scan, though it never names or explicitly contrasts with any sibling.

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?

There is no explicit statement of when to use this instead of alternatives like injection_scan or extract_contacts, so tool selection is left to inference from the detection list. However, it does provide concrete invocation guidance for the x402 payment flow, telling the agent the first call returns payment requirements and how to retry with an X-PAYMENT or PAYMENT-SIGNATURE header — that is operational guidance, not selection guidance.

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