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

Annotations already declare readOnlyHint=false, destructiveHint=false, idempotentHint=true and openWorldHint=false, so the safety profile is covered. The description adds only the defaulting behavior (account unit unless overridden), which is useful but thin; it never explains what happens on a duplicate log despite the idempotent hint, nor what the tool returns on success.

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?

A single sentence with the action front-loaded, followed by the example and the unit-default rule. No filler or redundant restatement of the title.

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 simple four-parameter write tool with full schema coverage and clear annotations, the description covers what to log and how the unit defaults. The remaining gap is post-write behavior (what confirmation or identifier comes back, and how idempotency applies), which matters only because there is no output schema.

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 value, note, time and unit are all already documented, including the 'see get_profile' pointer for the account unit. The description's unit clause restates the schema rather than adding new meaning, so 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 names a specific verb and resource ('Log a glucose reading') and anchors it to the user's own measurement with a concrete utterance example ('I just measured 120'). That makes it clearly distinct from the retrieval sibling get_glucose and from the other log_* tools, which cover different resources.

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 example phrasing gives a clear trigger condition: invoke this when the user reports a fresh measurement. It does not explicitly rule out alternatives (e.g., use get_glucose to read history, or another log_* tool when the measurement is insulin/meal related), so the guidance is clear but not exhaustive.

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