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

Annotations already declare this is a non-read-only, non-destructive, closed-world write, so the safety profile is covered. The description usefully adds the consequential side effect that the newest reading becomes the current weight and drives calorie targets. However, it is silent on how backdating via logged_at interacts with 'newest reading', and whether a same-day entry replaces an earlier one.

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 sentences, zero filler, with the primary effect front-loaded and the downstream consequence in a parenthetical. Nothing redundant with the schema or annotations.

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 mutation tool with no output schema and 4 parameters, the definition covers purpose and the main side effect but leaves the agent without knowledge of what is returned or how re-logging/correcting an existing weigh-in is handled. That is an incomplete picture for a write operation.

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 50%, and the two documented parameters (logged_at, tz_offset_min) are well specified in the schema itself. The description compensates for the largest gap by declaring weight_lb is in pounds, which the schema does not state; only the free-form 'note' parameter goes unexplained.

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 verb (log) plus resource (weigh-in) and immediately disambiguates from siblings like log_water, log_exercise, and log_anything by naming the exact domain concept. The unit ('in pounds') is stated up front, which no other field supplies.

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?

Usage is implied rather than stated: an agent can infer this is the tool for recording a body weight, but nothing says when to prefer update_log for corrections or how log_anything differs. No exclusions or prerequisites are given.

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