downloadActivityFit

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

With no annotations, the description carries the burden and does disclose the key non-obvious trait: this is a disk-writing operation that saves a file to the user's machine and returns the absolute path. It also summarizes the payload contents. It omits overwrite behavior, whether the destination directory is fixed, and permission/error cases.

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?

Two short sentences, front-loaded with the action and side effect, followed by the return value. No filler; every clause carries information.

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 single-parameter, no-output-schema tool, the description covers the action, the side effect, and the return value, which is sufficient to call it correctly. It stops short of stating where the file lands or what happens on repeated downloads.

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?

Only one parameter exists and schema description coverage is 100% ('Garmin activity id'), so the schema already fully documents it. The description adds no format, sourcing, or lookup guidance for activityId beyond what the schema provides.

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 states a specific verb and resource ('Download the ORIGINAL .FIT file of an activity') and emphasizes 'ORIGINAL' plus 'save it on the user's computer', which separates it from metadata readers like getActivity or getActivityLaps. It does not explicitly name a sibling, so an agent must infer the boundary.

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?

Usage is implied: fetch the raw file when second-by-second data is needed locally, rather than the parsed summaries returned by getActivity/getActivityLaps. There is no explicit when-to-use / when-not-to-use statement or named alternative, leaving the routing to inference.

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