Measure the plan

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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safe read-only nature is covered. The description adds useful defaults (z band 0-200) and hints at output shapes, but does not elaborate on behavioral traits like performance or interpretation of edge cases beyond what annotations and the output schema supply.

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?

It is tightly packed but presented as one undifferentiated paragraph covering four distinct modes, which hurts front-loading and scannability. Most sentences earn their place, but structural separation of modes would materially improve it.

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?

With an output schema present and 100% schema coverage, the description only needs to convey mode selection and defaults, which it does. The main gap is the absence of explicit guidance on when NOT to use this tool versus siblings such as layout.

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 100%, so the baseline is 3, but the description goes beyond the schema by explaining how parameters combine (from alone vs from+to vs axis+at vs gap+grow) and what each combination returns. It adds real combinatorial meaning over the per-parameter descriptions.

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 states a specific verb+resource ('Tape measure over the plan, in cm') and enumerates the distinct measurement modes (from alone, from+to, axis+at, gap+grow). It is clearly distinguishable from siblings like layout or move, though the dense prose requires careful reading to extract the core purpose.

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 effectively tells the agent when each parameter combination applies, describing the question each mode answers (e.g. 'the answer to how wide is the corridor here' and 'the question a layout decision actually ends in'). It does not name an alternative sibling or state explicit exclusions, keeping it short of a 5.

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