Redact regions in a local image

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

With annotations declaring a non-readonly, non-destructive write, the description adds real context beyond them: the operation is permanent, output is a flattened PNG, source metadata is not copied, every decoded output pixel is verified, and a local browser is required. It does not state that transparency/color profile may be lost or how out-of-bounds regions are reported, keeping it just 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?

The effect and permanence are front-loaded in the first sentence, followed by inputs, outputs, verification and limits in a tight sequence with no filler. It reads as a dense list of clauses, which is efficient but slightly terse to scan.

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 3-parameter write tool with no output schema, the description covers effect, accepted formats, output format, metadata handling, verification and the browser prerequisite. Remaining gaps (error behavior for mismatched dimensions or non-fitting rectangles) are partially covered by the schema.

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 100% and the schema already documents all three paths and the JSON region format in detail. The description only restates that dimensions and rectangles come from a local JSON file, so it adds little beyond the schema; baseline 3 applies.

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?

"Permanently replace explicitly selected image rectangles with opaque black pixels" gives a precise verb, resource and effect, and no sibling tool performs redaction, so it is unambiguous against the surrounding compress/resize/convert family. The follow-on sentence naming the accepted input formats and PNG output further pins down the operation.

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?

It makes clear the regions must be chosen in advance and supplied via a JSON file, and explicitly says it "Does not detect sensitive content or prove the chosen regions cover it," which steers an agent away from expecting auto-detection. No sibling is named as an alternative, but none exists, so guidance is effectively complete for the context.

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