Read explicit swim lengths and grouped sets

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

With no annotations, the description carries the full burden and does substantial work: it discloses source-awareness, reports missing length lists as unavailable, and explicitly guarantees no reconstruction from samples. It omits output structure and error behavior, but the core behavioral contract is unusually clear for a read tool.

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 dense sentences with no filler. Primary behavior is front-loaded, followed by an edge-case guarantee and a prerequisite. Every sentence adds distinct value.

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 tool with no output schema and no annotations, the description covers the main return concept, the unavailable case, and a key prerequisite. It omits provider-default behavior and activityId provenance, but those are moderate gaps rather than fatal ones.

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 0%, so the description must compensate, but it only meaningfully documents athleteId via 'Requires athleteId from list_athletes' and indirectly hints at provider through the Garmin/Intervals.icu naming. The optional provider semantics, its default when omitted, and activityId are left undocumented.

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 ('Return') and names the exact resource ('source-aware swim lengths', 'Garmin detected and Intervals.icu auto-detected sets'), plus clarifies a key non-behavior ('laps are never reconstructed from samples'). This clearly distinguishes it from sibling read/analytics tools.

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 the triggering condition ('when a provider actually supplied them'), an exclusion ('never reconstructed from samples'), and a prerequisite ('Requires athleteId from list_athletes'). However, it does not name alternative tools such as get_activity_segments or swim_progress_report, so cross-tool routing is not fully explicit.

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