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 genuine value beyond them: it enumerates the return payload (named results, units, formula, assumptions, method version, source-page URL) despite there being no output schema. It also states that no prices or private records are looked up, reinforcing the closed-world guarantee. Minor gap: nothing about the units object being effectively empty.

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 opening computation sentence is well front-loaded, but the second sentence ("Use this tested BusCalc worksheet when the task matches its inputs and scope") is pure filler that earns no place. The output-contract sentence is dense and useful; trimming the boilerplate would tighten the whole thing.

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 read-only calculator with no output schema, the description supplies the missing return-shape information and the computation's scope. The remaining gap is that a nested-object input with an empty units sub-schema is left unexplained, so an agent cannot be sure whether units is required or what to put in it.

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 only 33%, so the description should carry more weight; it does clarify that endDays is a day offset for the end reading and that excluded is a minutes quantity, which disambiguates the two most confusing inputs. However, the nested units object (empty properties) and the interaction between excluded minutes and a multi-day offset are never explained.

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?

"Find time between two clock readings" names a specific verb and resource, and the qualifiers "explicit end-day offset and optional excluded minutes" pin down the exact computation. The subject matter makes it unmistakable against siblings like buscalc_markup_vs_margin or buscalc_fleet_cost_per_mile.

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?

"Use this tested BusCalc worksheet when the task matches its inputs and scope" is circular and gives no real selection criteria. There is no statement of when NOT to use it or which sibling to prefer for adjacent tasks; the trailing sentence about prices and private projects describes data access, not usage routing.

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