Garmin Activity Series

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

The description discloses key behavioral traits beyond the annotations: 'Returns exact stats computed on full-resolution samples plus a downsampled series capped at 500 points' and the context-window rationale ('never blows the context window'). It also reinforces the GPS exclusion. These details add genuine value beyond the readOnly/idempotent 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?

Three sentences, each earning its place: first states purpose, second explains behavior and rationale, third gives usage guidance and an exclusion. No filler, front-loaded with the core concept, and ends with a clear boundary.

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?

With a rich output schema, six parameters (most well-documented in the schema), and annotations covering safety, the description is complete. It explains the tool's purpose, when to use it, its output constraints (downsampling cap, no GPS), and the context-window benefit. No critical gaps remain.

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 high (83%) and the schema already explains most parameters. The description adds contextual meaning by framing the tool as a 'bounded time-series' and referencing the 500-point cap, which directly informs max_points and resolution_seconds semantics. That extra layer justifies a score above baseline.

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 opens with a specific verb+resource: 'Bounded time-series for one activity metric.' It clearly distinguishes itself from siblings by name-dropping alternatives ('Prefer garmin_get_activity / splits / hr_zones first') and stating its unique value ('when you actually need the shape of the effort over time').

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?

Explicit when-to-use guidance is provided: 'Prefer garmin_get_activity / splits / hr_zones first; reach for this when you actually need the shape of the effort over time.' It also states a clear exclusion: 'GPS is never returned here.' This gives the agent actionable selection criteria.

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