count_activities

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

Annotations only cover readOnlyHint and openWorldHint, so the description adds real value by disclosing error behavior (throws `GarminError` on empty or non-numeric `totalCount`) and clarifying the narrowed return value. This is meaningful beyond the safety hints.

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?

A single front-loaded sentence with no filler, stating the return value first and the failure mode second. Dense but efficient; every clause earns its place.

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 zero-param read tool with no output schema, the description adequately explains what is returned and how it fails. It leaves the scope of the count (all-time vs. filtered) unstated, a minor gap.

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 document; baseline 4 applies. No parameter guidance is needed or expected.

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?

Combined with the name, the description states a specific behavior: it returns the envelope's `totalCount` rather than the whole payload, implicitly distinguishing it from `get_activities`. It never explicitly says 'counts activities' in prose, but the resource and result are 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?

The phrase 'not the whole response' implies you should pick this over the full-response siblings when only a count is needed, but no explicit when-to-use or named alternative is given. Usage is only implied.

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