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

Annotations already cover the safety profile (readOnly, non-destructive, closed-world). The description adds genuinely new behavioral context: the default-to-today behavior and the free-plan gating that returns days older than 7 days as locked — a return-shape caveat the agent could not infer from annotations.

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?

Three sentences, each earning its place: return shape first, intended use second, plan-limit caveat last. Dense and front-loaded with no filler.

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 still specifies what comes back (per-day net carbs, target comparison, meal counts, locked days) plus the parameter default and access gating. Nothing an agent needs to call and interpret it correctly is 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?

Schema coverage is 100% and the single `end` parameter is fully documented with format and timezone. The description only restates the default-today behavior, adding little beyond the schema, 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?

States a specific resource and aggregation: 'Daily net-carb totals for the 7 days ending on a date ... with the number of meals each day.' The 7-day window plus per-day breakdown clearly separates it from the sibling get_day's single-day scope without needing to name it.

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?

Gives an explicit use case with an example question: "Use it for trends ('was I over this week?')", which tells the agent the trend-analysis intent. No exclusion or when-not guidance, and siblings like get_day are not named as alternatives, so it stops short of a 5.

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