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

With readOnlyHint=true already declaring the safety profile, the description adds genuinely new operating context: the $0.004 USDC x402 per-call cost, the Luhn/checksum validation methods, and the 12,000-character cap in names mode. It does not disclose whether the submitted text is stored or transmitted, which matters for a PII tool, so it stops short of a 5.

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 operation and its use case, then modes, then pricing. The long entity-type enumeration is dense but each item earns its place by telling the agent what will be caught. Slightly more compact formatting (modes/pricing split out) would be cleaner.

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 single-text, read-only tool with no output schema, the description covers inputs, modes, validation depth, and cost. The one notable gap is what the caller gets back in detect vs redact mode (labels, spans, counts), though the mode names imply it.

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 80%, so the baseline is 3, and the description adds real value on top: it explains what each mode produces ('redact with consistent labels, mask, or detect only'), clarifies that names=true uses AI and carries a length limit, and implies the types/country parameters through the enumerated type list and region mention.

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 precise verb+resource ('find and redact personal and secret data') and enumerates exactly which entity types are covered, including the detection techniques (Luhn, IBAN checksum). This clearly separates it from siblings like moderate, regex, or extract that an agent might otherwise reach for.

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?

Gives a concrete usage context — 'before text goes to a model or a log' — which implies when this tool belongs in a pipeline. It does not name alternative tools or explicitly state when not to use it, but the triggering condition is clear.

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