garmin_api_download_activity

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

Adds real value beyond the annotations: it writes a new file on the local machine, targets a private directory, never extracts the archive, and returns file metadata rather than parsed content. It does not state overwrite behavior or name the destination path, which is the remaining gap for a filesystem-writing 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?

The first two sentences are well front-loaded and earn their place, but the closing sentence about 7-day defaults and a 31-day cap refers to date ranges that do not exist in this tool's schema (only activity_id is accepted), which is stale or copied boilerplate that adds noise without applying.

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?

An output schema exists, so return values need no explanation, and the description covers the write side effect, no-extraction behavior, and un-normalized payload. Missing only destination details and overwrite semantics, which are minor given the annotation set.

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 0% for the single required activity_id, and the description never explains it. That said, the parameter is a single unambiguous integer whose meaning is clear from the tool name and 'the original activity ZIP,' so nothing is seriously misleading.

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?

States a specific verb and resource ('Download the original activity ZIP') and immediately scopes it with 'to a private local directory' plus 'never extracts the archive.' The phrase 'Raw JSON fields are not normalized' implicitly separates it from the JSON-returning siblings like garmin_api_activity and garmin_api_activity_search.

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 implies the use case (you need the untouched ZIP, not normalized data) and points to activity search pagination as the alternative for enumerating activities. However, it never explicitly says when to prefer this over garmin_api_activity or garmin_api_activity_workouts, so the routing is inferred rather than stated.

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