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

Annotations already mark this as a write operation (readOnlyHint=false) that is non-destructive, and the description adds real context beyond that: premium entitlement, the default per-call confirmation (and that it can be switched off), the user-confirmation requirement, and the Cotlet API key with app access. The 'Reaches other people' line is somewhat generic/odd for a private diary copy, but it adds a safety directive rather than contradicting the 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?

The purpose is front-loaded, which is good, but sentence 2 largely restates sentence 1 ('Transfers all meals from one day to another, the same as Copy Day in the app'), creating redundancy. The trailing confirmation and API-key sentences are useful but make the block longer than needed.

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 two-parameter copy tool, it covers the essentials: premium gate, confirmation behavior, auth requirement, and a verification follow-up (get_diary). With no output schema, it does not describe the return, but the confirmation and auth details compensate for the low-complexity surface.

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?

With 100% schema description coverage, the schema already documents from_date and to_date as YYYY-MM-DD. The description reinforces the direction of the copy ('one day to another day') but adds no syntax, defaults, or edge-case semantics 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 verb and resource: 'Copy all meals of one day to another day,' with scope (all meals, day-to-day) that clearly separates it from sibling tools like get_diary, log_food, or log_quick_entry. It also names the in-app equivalent (Copy Day) and the premium gating, so an agent knows exactly what this does.

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 concrete use context ('repeat a plan ahead of time') and routes the agent to a follow-up sibling, get_diary, to verify the target day. It states the premium requirement but does not spell out clear when-not-to-use exclusions, so it falls slightly short of a full routing rule.

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