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

Annotations already declare readOnlyHint=true and destructiveHint=false, so safety is covered. The description adds real behavioral context the annotations cannot: the cost model ($0.005 USDC per call via x402, client-paid) and that failed calls are not charged, plus the per-class breakdown of what gets detected.

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?

Three tight sentences: purpose first, then return shape, then billing caveat. Every sentence carries information an agent needs, with no filler.

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?

No output schema exists, and the description does a good job covering return values and cost. However, for a tool with an empty object schema, the description never explains the input pathway, leaving the agent unsure how to actually pass text for redaction.

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?

The input schema has zero declared parameters, so the baseline is 4. The description does not explain how the text to be redacted is actually supplied to a parameterless tool, which is an unresolved gap, but it does enumerate the PII classes driving the detection output.

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 ('Redact PII from text') and names the exact scope. It is clearly distinguishable from siblings like classify, extract, and normalize because it explicitly says it returns redacted text plus spans and counts.

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 clear usage context ('before it is stored or logged'), which tells the agent when this tool belongs in a pipeline. It does not name exclusions or point to an alternative sibling, so it stops short of full routing guidance.

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