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

Beyond the annotations (readOnlyHint=false, openWorldHint=true), the description adds a key behavioral detail: 'ok=true only after Garmin re-read shows the new values.' This tells the agent about the external verification step and success condition. It does not contradict annotations, and it provides valuable context about side effects and confirmation.

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 sentences, each earning its place: the action, the prohibition, the identification preference, and the success condition. It is front-loaded with the core purpose and contains no filler or repetition.

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?

Given the tool's complexity (16 parameters, 0 required, output schema present, annotations covering safety), the description provides the essential usage context but omits one helpful clarification: whether this is a partial update (only provided fields changed) or requires a full replacement. The schema implies optionality, yet explicit statement of partial-update semantics would improve completeness. Overall it is adequate but not comprehensive.

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 description coverage is 100%, so the parameters are already well-documented. The description adds only one param-related guideline ('Prefer log_id from list_nutrition'), which is useful but limited. Most of the meaning is carried by the schema, so a baseline score of 3 is appropriate.

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 uses a specific verb ('Change') and resource ('an existing food'), and explicitly states 'Do not add a second entry', which distinguishes it from log_nutrition. It also names the preferred way to identify the entry (log_id from list_nutrition), making its purpose unambiguous.

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 clearly indicates when to use this tool: when modifying an existing entry rather than adding one. 'Prefer log_id from list_nutrition' gives a concrete selection rule. However, it does not explicitly name alternatives or state conditions for when not to use this tool beyond the add/update distinction.

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