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

Annotations already declare the non-read-only, non-idempotent profile, and the description meaningfully extends it: it warns against retrying an uncertain result (consistent with idempotentHint=false), states the created record is private, and requires surfacing serviceAnnouncements from the named operator in every response. It does not explain post-creation visibility or error semantics, so it falls short of a 5.

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 short sentences, front-loaded with the action and scope, with no filler. The final sentence about serviceAnnouncements is long but carries an operational obligation rather than padding.

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 7-parameter mutation tool with zero schema descriptions and no output schema, the definition leaves several required inputs unexplained (time format, activity type vocabulary, unit expectations), so an agent cannot construct a valid call from the description alone. The confirmation, time zone, retry, and announcement rules are good but cover only part of the surface.

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% across 7 required parameters. The description clarifies only two of them implicitly: the confirmation precondition ('confirmed') and the IANA format expectation for timeZone, which does add value beyond the bare string type. It says nothing about startTimeLocal format, activityType valid values or their relation to garmin_activity_types, distanceMetres units, or durationSeconds units.

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 plus a scope qualifier: 'Create a private manual completed activity'. That distinguishes it from the sibling upload/update tools well enough to act on, though it never names the contrasting tool (e.g. garmin_upload_activity) explicitly.

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 conditions are stated as constraints rather than routing: 'after explicit confirmation', 'Use the activity's IANA time zone; do not assume one', 'Do not retry an uncertain result'. These are helpful preconditions, but there is no guidance on when to choose this tool over garmin_upload_activity or garmin_create_workout.

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