CGM glucose now

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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, covering the safety profile. The description adds that the trend arrow is included 'if available', which is useful, but it does not disclose potential latencies, connection requirements, or whether the value is cached. Given the annotations, the description adds minimal extra behavioral context, so a 3 is appropriate.

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, tightly worded sentence that front-loads the core function (returning the EGV) and the optional trend arrow. There is no filler, and every word earns its place, making it highly efficient and scannable.

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 no output schema, the description must convey the return value, and it does state the key output (EGV and trend arrow). It omits details like units (mg/dL vs mmol/L) and timestamp, but for a simple getter with a single optional parameter, this is largely sufficient for an agent to call it correctly. A more complete description might mention units or error cases, but it is not critically missing.

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?

The sole parameter, privacy_mode, is fully described in the schema with an enum and explanatory text, achieving 100% coverage. The description does not mention this parameter at all, so it adds no semantic meaning beyond what the schema already provides. Since the schema carries the full burden, the baseline of 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 uses the specific verb 'Returns' and clearly identifies the resource as 'most recent EGV' with an optional 'trend arrow'. This precisely distinguishes it from siblings like cgm_glucose_window (which implies a time range) and cgm_daily_summary (which implies aggregation), leaving no ambiguity about what the tool does.

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 does not provide explicit guidance on when to use this tool versus alternatives such as cgm_glucose_window for historical data or cgm_daily_summary for daily aggregates. It implies a single-point current reading via 'most recent', but it lacks exclusions or prerequisites, so an agent may not know the optimal selection context.

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