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

Annotations already provide readOnly, idempotent, and non-destructive hints, so the safety profile is covered. The description adds meaningful behavioral context beyond annotations: it uses published factors, A1c follows the NGSP↔IFCC master equation, and A1c also returns estimated average glucose. It does not describe the full output shape, but this is minor for a simple read-only conversion.

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 description is a single, front-loaded sentence with no filler. Every part earns its place: the action, the scope, the examples, the method, and the A1c exception.

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 low-complexity, read-only conversion tool, the description combined with the schema gives an agent enough to select and invoke it correctly: required parameters, direction default, analyte examples, and special A1c behavior. A full analyte list or explicit return-shape statement would be a minor enhancement, but the essential guidance is present.

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 all three parameters well. The description reinforces analyte semantics with examples and the 30-analyte limitation, but it does not substantially elaborate on the value or direction parameters beyond what the schema already provides. Baseline 3 is appropriate.

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 ('Convert'), a clear resource ('a lab value between US conventional and SI units'), and a concrete scope ('30 common analytes' with examples). It inherently distinguishes itself from all siblings, none of which perform unit conversion.

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?

The description implies when to use the tool: whenever a lab value needs US↔SI conversion for one of the 30 common analytes, with special A1c behavior. However, it does not explicitly mention alternatives or state when not to use it, such as when needing free testosterone calculation or reference range lookup.

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