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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint, so the safety profile is known. The description adds valuable behavioral details: deterministic matching, overlap-safe handling, and strict validation (Luhn, checksums, structural validity) that go beyond the schema. It does not contradict annotations; 'redact' is a pure transformation in this context.

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?

A single, dense sentence conveys all essential information without repetition or filler. It front-loads the core action and then lists precise details, making it highly scannable.

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?

Given the tool's moderate complexity, the description covers the key behavioral aspects (determinism, supported types, validation rigor, overlap safety) and is supported by a rich input schema and output schema, so an agent has enough context to invoke it correctly. The only minor gap is the omitted 'types' default, but that is not critical given the schema and description.

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 0%, so the description must compensate. It does so by clarifying what 'types' supports (emails, phones, IPs, cards, IBANs, SSNs) and by adding validation semantics like 'validated IPv4/IPv6' and 'Luhn-valid payment cards'. However, it does not state the default behavior when 'types' is omitted, leaving some ambiguity.

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 uses a specific verb ('detect and redact'), names the resource ('PII and personal data in supplied text'), and enumerates exact detection categories. It clearly distinguishes this tool from sibling tools like document.extract or data.clean by emphasizing deterministic redaction with validated matching.

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?

The description gives clear context for when to use the tool: when PII redaction is needed with deterministic, overlap-safe matching for specific entity types. It does not explicitly name alternatives or state when not to use it, so it stops short of a perfect score.

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