get_lifetime_totals

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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=true, so the "read-only" restatement and the Garmin Connect attribution add little. Nothing is said about how costly the call is, whether data is pre-aggregated server-side, or the freshness of the totals, which would be genuinely new behavioral information.

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?

It is short and front-loaded with the purpose, but the trailing parenthetical mixes the useful metric list with boilerplate ("Garmin Connect, read-only") and a date-format caveat that cannot apply to a zero-parameter call. The "..." trailing the field list leaves the return contents vague for no size savings.

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 zero-argument read with an output schema and full annotations, the description covers what is needed: what it returns at a high level and that it is a safe read. The output schema carries the exact field list, so omitting return detail is appropriate; only competitor routing is thin.

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?

The tool takes zero parameters, so the schema-based baseline is 4 and there is nothing for the description to disambiguate. The appended "Dates are YYYY-MM-DD" note maps to no parameter here and is inert rather than helpful.

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 gives a specific verb ("Return") and resource ("lifetime totals") and enumerates example fields, so an agent knows it is an aggregate-since-account-creation endpoint rather than a per-day or date-range one. It does not name or contrast with siblings like get_user_statistics or get_progress_summary_between_dates, which is the remaining gap.

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?

The word "lifetime" implicitly tells the agent to pick this over date-scoped tools, but there is no explicit when-to-use/when-not statement and no reference to the closest alternatives (get_user_statistics, get_progress_summary_between_dates). Usage must be inferred from scope wording alone.

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