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

readOnlyHint=false already tells the agent this is a mutation, and the description adds a genuinely non-inferable behavior: the call is confirm-gated and previews unless confirm: true. That is exactly the kind of two-phase semantics an agent could otherwise get wrong. It stops short of saying what the preview contains or whether logging notifies the client, which keeps it off a 5.

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 sharply front-loaded clauses with zero filler: the action first, the gating mechanic second in parentheses. Nothing is repeated from 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 wrapping a twelve-field nested payload with no output schema, the description leaves too much open: no mention of what the preview returns, whether a second call is required, whether macros/calories are required or optional, or how planMealOrder ties to planId. The confirm gate is well handled, but the rest of the call surface is unexplained.

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?

The description only touches the `confirm` flag; it says nothing about the `input` object, which carries twelve nested fields including ambiguous ones like source (PLANNED vs EXTRA), compliance (ON_PLAN/OFF_PLAN/PARTIAL), planId, and planMealOrder. With coverage at 50% and the undocumented half sitting inside a nested object, the description does not compensate for the schema gap.

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?

The description pairs a specific verb ("Log") with a specific resource ("a meal") and a scope qualifier ("for a client on their behalf"), which separates it from read-side siblings like get_client_diet_logs or list_client_saved_meals. It does not explicitly name a sibling to disambiguate against log_client_habit / log_client_workout, but the resource noun does that work implicitly.

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?

There is no statement of when to use this versus the other client-logging tools or versus a client self-logging flow, and no prerequisites (e.g. does the client need an active plan?). The only usage-shaped sentence is the confirm gate, which is a mechanics note rather than guidance on when to choose this tool.

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