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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so the bar is lower. The description then adds real behavioral context: results come in both metric and US units with an uncertainty band, closure and crossing checks, plus a canvas link, and it flags that no image is ingested.

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 front-loaded sentence opening with the verb, with no filler. It is dense — parenthetical units, reference types and output features packed into one clause chain — but every element carries information.

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 6-parameter nested tool with an output schema, the description supplies the essential mental model: what is measured, what inputs it expects, that a reference is mandatory, and that no image is passed. The remaining gap is routing guidance against sibling measurement tools.

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%, so the schema already documents every parameter including the reference object, pixelError, detail and system. The description only restates the conceptual contract (points plus one known reference), adding no syntax or format detail beyond the schema — the 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?

The description names a precise verb+resource+scope: it measures areas, perimeters and lengths from pixel points plus one known reference, and it explicitly notes it receives no image. That last clause cleanly separates it from image-consuming siblings like run_takeoff or create_project_file_from_plan.

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?

Usage is only implied: the agent can infer it should call this when it already has point coordinates and a reference scale, and the 'It receives no image' clause rules out image-input workflows. There is no explicit when-to-use, no when-not, and no named alternative among the many measure/takeoff siblings.

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