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

Annotations already declare readOnlyHint=false and destructiveHint=true, so the mutation/safety profile is partly covered. The description adds genuine beyond-annotation context: the mutation scope is limited ('Meals are not changed'), null is a clear operation, and there is a post-condition workflow rule ('Confirm the change only after success'). It stops short of naming auth requirements or return behavior, but the added value is real.

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?

Four tight clauses separated by semicolons, each carrying a distinct payload (state triggers, prohibition, side-effect scope, confirmation rule). Front-loaded and free of 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 an output schema present, return values need not be described. The description covers trigger conditions, exclusions, side-effect scope, and success handling, which is everything an agent needs to call this two-required-parameter mutation correctly.

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 both parameter descriptions already explain partial/complete/null semantics, so baseline is 3. The description largely restates the same value meanings, adding only mild elicitation context rather than new syntax or format detail.

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 ('Mark a day') plus the exact resource and the three possible states (partial/complete/null-clear). It is immediately distinguishable from the meal-oriented siblings (create_meal, update_meal) because the description makes clear only the day status is touched.

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 explicit when-to-use conditions for each state ('partial when the person says they ate things that day they did not log', 'complete when they confirm everything was logged') and an explicit when-NOT-to-use rule ('Never mark a day only because its total looks low: ask first'). Nothing is left to inference.

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