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

Annotations already cover the safety profile (readOnlyHint, openWorldHint), so the bar is lower; the description still adds the subscription gating requirement and discloses the fixed result count (13 units) and endpoint. That is meaningful context beyond 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 content is short but redundant: 'Requires a Garmin Connect+ subscription' and the trailing 'Needs Connect+' restate the same fact, and the raw endpoint adds little for an agent. Front-loading is acceptable but the repetition wastes the limited space.

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 parameterless metadata read with no output schema, the description supplies the essential gating (subscription check) and the nature of the return (a set of ~13 serving units). Nothing critical is missing for correct invocation.

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 tool takes zero parameters, so there is nothing for the description to disambiguate and the baseline is 4. No misleading parameter guidance is present.

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 names the specific resource ('serving units a custom food can use') and the underlying endpoint, distinguishing it from siblings like get_custom_foods and create_custom_food. It is clear what is retrieved, though the phrasing is slightly clipped rather than a crisp verb+resource statement.

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 a prerequisite (Garmin Connect+ required) and points to the has_connect_plus sibling to verify it, which is useful routing. However, it never explains when an agent should call this versus other nutrition metadata lookups, so usage context is only implied.

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