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

Annotations already declare this is a non-destructive, non-idempotent write, so the safety profile is covered structurally. The description adds nothing behavioral - no note on what happens on duplicate submissions, a missing permission, or how the `idempotency_key` affects retry behavior, which is notable given idempotentHint=false.

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 tight sentences with the primary action front-loaded and no filler. Efficient for the amount of information conveyed, though it could carry a bit more without becoming bloated.

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 5-parameter mutation tool with no output schema and 0% schema coverage, the description leaves significant gaps: the semantics of `at` (timestamp?) and `idempotency_key` are never addressed, and no behavioral context accompanies the write.

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 0%, so the description must compensate, and it does explain the kind→unit constraint pairs (weight→kg/lb, length→cm/in), which is genuinely useful information absent from the schema. However `at` and `idempotency_key` are completely undocumented in both schema and description, leaving two parameters 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?

Specific verb+resource ("Log a growth measurement") that clearly separates it from log_feed, log_nappy, log_sleep, and log_supplement. The clarification that `kind` is weight or length sharpens the scope, though it doesn't explicitly name a competing sibling.

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?

No when-to-use or when-not-to-use guidance and no mention of alternatives such as undo_last for correcting an entry. The description only restates the operation, leaving context entirely to inference.

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