Count Activities

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

The annotations already declare readOnlyHint and openWorldHint, so the agent knows this is a safe read operation. The description adds the behavioral nuance that the count spans the user's entire Garmin Connect history unless a start/end date is supplied, which is useful beyond the annotations. It doesn't discuss the exact return value shape, but for a simple count tool this burden is low.

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 description is a single sentence that leads with the action and resource, then quickly covers the scope alternatives. There is no redundant phrasing or extra detail, making it an excellent concise description.

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 simple two-parameter optional read-only tool, the description plus schema gives the agent enough understanding to invoke it. Because there is no output schema, the description could arguably state that the result is a number, but the name and purpose already imply a count, so this is 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?

Schema description coverage is 100%, with each parameter already documented as optional, date-formatted, and providing defaults. The tool description merely restates the 'date range' concept already covered by the schema. It doesn't add additional param semantics, so the baseline 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 ('Count') with a clear resource ('activities in Garmin Connect') and explicitly defines the scope as 'whole history' or 'date range'. This purpose is distinct from sibling tools like list_recent_activities or get_activity_details, which retrieve lists or single activity details rather than aggregate counts.

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 description clearly states when this tool is appropriate: for counting activities across all history or for a bounded date range. It does not explicitly name alternatives like list_recent_activities for retrieving details, but the context makes it clear that count_activities is intended for counts rather than item-level data.

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