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

readOnlyHint=true already tells the agent this is a safe read, so the description's job is to add context. 'Lifts are stored in kg' is genuinely useful behavioral information about the underlying data model, but the description doesn't say what happens if the client has no unit configured (default value?) or how the value is returned.

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 short sentences with zero waste; the identity of the value comes first and the kg-storage caveat follows. Nothing could be removed without losing meaning.

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 one-parameter read-only tool with no output schema, the description is nearly complete — it even states the domain of return values. The only missing piece is the fallback behavior when no display unit is set.

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% and the single clientId parameter is fully documented in the schema, including where to obtain it (from list_clients). The description adds nothing about the parameter, so 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 the specific resource — the client's display unit for weights — and enumerates the possible values (kg or lbs). It is clear enough to distinguish from unrelated siblings like log_managed_client_weight, but it doesn't differentiate itself from get_client_preferences, which plausibly also exposes this setting.

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?

There is no explicit when-to-use or when-not-to-use guidance and no named alternative. The line 'Lifts are stored in kg' implies the intended context (convert stored values for display), but the agent must infer that rather than being told.

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