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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so safety is covered. The description still adds real behavioral detail beyond them—the default resolution of a null date to today and the breadth of what comes back (including derived totals and a weight trend)—though it says nothing about permissions or pagination/limits.

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 tightly packed sentences, front-loaded with the triggering condition and closed with the exclusion. The middle sentence's itemized payload list is slightly long given an output schema exists, but every element is informative rather than 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?

For a one-parameter read tool with an output schema and full annotation coverage, nothing an agent needs is missing: trigger conditions, the null-date default, and the alternative for writes are all present.

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 single parameter has no description, so the description does the work: 'date null is today' tells the agent the nullable default, which is the one semantic that matters here. It does not cover date-range boundaries or timezone handling, keeping it short of a 5.

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 gives a specific verb and resource ('Reads a day's food') and enumerates the payload: entries with ids, totals vs. targets, usual foods, saved recipes, weight trend. It explicitly separates itself from log_foods, so an agent can pick it without opening the 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?

It states exactly when to reach for it ('when the person asks what they've eaten or how their calories and protein are going') plus a non-obvious precondition (before removing a logged food), and names the exclusion and its replacement: 'Do not use to log food; use log_foods.'

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