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), and the description adds genuinely non-obvious context: the grouping comes from 'the site's own keyword rule over each line's calculator or words,' and the result is advisory rather than authoritative. It does not discuss failure modes or rate limits, which keeps it out of the top band.

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?

Two sentences, front-loaded with the verb and the standard, and the trailing disclaimers ('not a specification,' 'no Uniclass or NRM,' 'no prices') each carry real information. The first sentence's stacked parentheticals are dense enough to slow reading slightly, so not a 5.

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?

An output schema exists, so return values need no explanation, and the description covers inputs, the classification mechanism, and the tool's limits. What remains implicit is how the three input modes interact if more than one is supplied and what an empty or unclassifiable line yields.

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 adds meaning the schema does not state outright: that `lines`, `calculators`, and `token` are alternative ways of supplying the same material set. It does not explain the `detail` enum beyond what the schema already says.

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 (groups) applied to a specific resource (materials list / bill / takeoff / plan / project) and names the classification standard (CSI MasterFormat 2018). It also enumerates the accepted input forms (lines, calculator slugs, project state token), which no sibling tool does, so an agent can distinguish it immediately.

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?

Explicitly frames the output as 'a suggested grouping, not a specification' and rules out Uniclass or NRM grouping and prices, which tells the agent when this tool is and is not the right fit. It stops short of naming an alternative tool for those excluded standards, so routing guidance is incomplete but clearly present.

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