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

Annotations already establish the safety profile (not read-only, not destructive, not idempotent), so the bar is lower. The description adds real behavior beyond that: the consistency value is silently recorded in the event note, and when it is `blood` or `mucus` the response includes a `safety_note` — genuinely useful non-obvious context.

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, front-loaded with purpose then parameter semantics then a behavioral caveat. No filler; the enum listings are necessary because the schema omits them, though they make the description slightly dense.

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?

No output schema, so return values need not be explained, and the description helpfully flags the `safety_note` behavior. But for a 5-parameter mutation tool with 0% schema coverage, three parameters remain wholly unexplained, leaving the definition incomplete.

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% and the schema lacks even enum constraints, so the description carries the full burden. It supplies the valid values for `kind` and `consistency` plus a conditionality rule — real added meaning — but leaves `at`, `note`, and `idempotency_key` entirely undocumented anywhere.

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) and resource (nappy change), cleanly distinguishing it from the sibling logging tools log_feed, log_sleep, log_measurement, log_supplement, and log_note. An agent can route to it without opening any schema.

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 implies usage by stating that `consistency` is only meaningful for `dirty`/`mixed`, which is a genuine conditional. However, it gives no explicit when-to-use guidance, no prerequisites, and no comparison to alternatives such as log_note for recording observations.

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