Activity detail

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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so safety is covered. The description adds genuinely new behavioral context: detail='full' returns Garmin's raw record with 200+ fields, which warns the agent about payload size and shape — something no annotation conveys.

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?

Front-loaded with the core purpose, then the field inventory, then the sibling routing, then the full-mode caveat — a sensible order with no filler sentences. The field enumeration is long but each item is a real capability; slight density cost only.

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?

There is no output schema, so the description carries the burden of describing returns — and it does, listing the metric families returned and delimiting the split-summary granularity. For a 2-parameter read tool with full annotation coverage, nothing an agent needs in order to call and interpret it is missing.

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 100%, so baseline is 3; the description goes slightly beyond it by quantifying the 'full' mode (200+ fields, 'Garmin's raw record') where the schema only says 'raw payload'. It does not, however, explain what is dropped in compact mode beyond 'meaningful fields'.

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?

Names a specific verb+resource ('One activity in detail') and then enumerates exactly what is returned: distance, times, pace, HR, cadence, running dynamics, power, training effect/load, temperature, RPE/feel, split summaries. It also explicitly separates itself from get_activity_analysis and from the raw 'full' variant, so an agent can distinguish it from siblings without opening a 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?

Gives a clear exclusion with the alternative named: split summaries here are warm-up/active/cool-down totals, 'not per-km; use get_activity_analysis for km/mile splits and laps'. It also routes to detail='full' for raw payloads. It does not spell out the typical search_activities -> get_activity flow in the description (that lives only in the schema parameter text), which keeps it short of a 5.

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